---
title: Identify the next term of the sequence 2, 5, 11, 23, ..., in which e… — Olympiad: thinking like a machine, Beb… · tree and pragmatics
description: Identify the next term of the sequence 2, 5, 11, 23, ..., in which each term is formed by doubling the previous term and adding one. Exam question 4 of lesson 31 «Olympiad: thinking like a machine, Bebras puzzles ★★★» of the AI course of Mova's primary school, with the dependency tree and pragmatics
---

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# Exam question 4 · Olympiad: thinking like a machine, Bebras puzzles ★★★

<!-- .ven lang=en -->
Identify the next term of the sequence 2, 5, 11, 23, ..., in which each term is formed by doubling the previous term and adding one.

<!-- .vintro -->
**Mova's choice:** option 1 · **The right answer:** option 3 · wrong ✗ · **Who acts:** you · **What happens:** identify, form, double, add, term · **To what, where:** next term, term, previous term, one, sequence

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This is exam question 4 of lesson 31 «Olympiad: thinking like a machine, Bebras puzzles ★★★» of the AI course of Mova's primary school, asked in stiff, formal language. The page gives the question's syntax tree — a dependency tree in the style of Universal Dependencies — and its pragmatics clause by clause, then the 4 options as the student saw them, each with its tree and pragmatics. Every text is parsed by Mova itself. How the student answered it, with the score of every option and why: [the test at school](https://md.mova.elamur.ai/free/en/school-run/ai/31-olympiad-thinking-like-a-machine/#e4).

## The question {#question}

```conllu
# sent_id = question:ai:31-olympiad-thinking-like-a-machine:e4:1
# text = Identify the next term of the sequence 2, 5, 11, 23, ..., in which each term is formed by doubling the previous term and adding one.
1	Identify	identify	VERB	VB	Mood=Imp|VerbForm=Fin	0	root	_	_
2	the	the	DET	DT	Definite=Def|PronType=Art	4	det	_	_
3	next	next	ADJ	JJ	Degree=Pos	4	amod	_	_
4	term	term	NOUN	NN	Number=Sing	1	obj	_	_
5	of	of	ADP	IN	_	7	case	_	_
6	the	the	DET	DT	Definite=Def|PronType=Art	7	det	_	_
7	sequence	sequence	NOUN	NN	Number=Sing	4	nmod	_	_
8	2	2	NUM	CD	NumForm=Digit|NumType=Card	7	flat	_	SpaceAfter=No
9	,	,	PUNCT	,	_	10	punct	_	_
10	5	5	NUM	CD	NumForm=Digit|NumType=Card	8	conj	_	SpaceAfter=No
11	,	,	PUNCT	,	_	12	punct	_	_
12	11	11	NUM	CD	NumForm=Digit|NumType=Card	8	nmod	_	SpaceAfter=No
13	,	,	PUNCT	,	_	14	punct	_	_
14	23	23	NUM	CD	NumForm=Digit|NumType=Card	12	conj	_	SpaceAfter=No
15	,	,	PUNCT	,	_	23	punct	_	_
16	...	...	PUNCT	,	_	23	punct	_	SpaceAfter=No
17	,	,	PUNCT	,	_	23	punct	_	_
18	in	in	ADP	IN	_	19	case	_	_
19	which	which	PRON	WDT	PronType=Rel	23	obl	_	_
20	each	each	DET	DT	PronType=Tot	21	det	_	_
21	term	term	NOUN	NN	Number=Sing	23	nsubj:pass	_	_
22	is	be	AUX	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	23	aux:pass	_	_
23	formed	form	VERB	VBN	Tense=Past|VerbForm=Part|Voice=Pass	1	advcl	_	_
24	by	by	SCONJ	IN	_	25	mark	_	_
25	doubling	double	VERB	VBG	Tense=Pres|VerbForm=Part	23	advcl	_	_
26	the	the	DET	DT	Definite=Def|PronType=Art	28	det	_	_
27	previous	previous	ADJ	JJ	Degree=Pos	28	amod	_	_
28	term	term	NOUN	NN	Number=Sing	25	obj	_	_
29	and	and	CCONJ	CC	_	30	cc	_	_
30	adding	add	VERB	VBG	Tense=Pres|VerbForm=Part	25	conj	_	_
31	one	one	NUM	CD	NumForm=Word|NumType=Card	30	obj	_	SpaceAfter=No
32	.	.	PUNCT	.	_	1	punct	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **identify** | imperative | you *not said here* | the next term of the sequence |  |  |  |  | vn characterize-29.2-1-1 «NP V NP S\_ING»: agent=Agent term=Theme |
| 2 | **form** | present · passive |  | each term |  |  |  |  | vn appear-48.1.1 «PP.location V NP»: subject=Theme |
| 3 | **double** | gerund |  | the previous term |  |  |  |  | vn other\_cos-45.4 «NP V NP.patient»: agent=Agent term=Patient |
| 4 | **add** *speech: assert* | gerund |  | one |  |  |  |  | vn mix-22.1-2 «NP V NP»: agent=Agent one=Patient |
| 5 | **term** |  |  | the sequence |  |  |  |  | nom term «communication transitive»: of=patient |

<!-- .note -->
One row per clause the reader finds. «not said here»: a role filled from the clause above. «roles by»: a VerbNet class and frame when one fits the verb, else the reader's rules on the tree.

## The options {#options}

### Option 1 · ← Mova's choice {#o1}

<!-- .ven lang=en -->
46

```conllu
# sent_id = question:ai:31-olympiad-thinking-like-a-machine:e4:o1:1
# text = 46
1	46	46	NUM	CD	NumForm=Digit|NumType=Card	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 2 {#o2}

<!-- .ven lang=en -->
35

```conllu
# sent_id = question:ai:31-olympiad-thinking-like-a-machine:e4:o2:1
# text = 35
1	35	35	NUM	CD	NumForm=Digit|NumType=Card	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 3 · ✓ the right answer {#o3}

<!-- .ven lang=en -->
47

```conllu
# sent_id = question:ai:31-olympiad-thinking-like-a-machine:e4:o3:1
# text = 47
1	47	47	NUM	CD	NumForm=Digit|NumType=Card	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 4 {#o4}

<!-- .ven lang=en -->
45

```conllu
# sent_id = question:ai:31-olympiad-thinking-like-a-machine:e4:o4:1
# text = 45
1	45	45	NUM	CD	NumForm=Digit|NumType=Card	0	root	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

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**Text:** the tests of Mova's primary school, written for Mova (`world/data/school/`), as the course runner gave them to the student. **Trees:** Mova's own parse — the `en` model on the CPU, when the site is built — not checked by a teacher; they may be wrong. **Frames:** Mova's frames reader (`prag`), each text read on its own. Elamur Cosmic License.

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- ← previous: [Olympiad: thinking like a machine, Beb…, exam 3](https://md.mova.elamur.ai/free/en/corpora/questions/ai/31-olympiad-thinking-like-a-machine/e3/)
- next →: [Olympiad: claims, clues and tricky mes…, test 1](https://md.mova.elamur.ai/free/en/corpora/questions/ai/32-olympiad-claims-clues-and-tricky-messages/t1/)
- ↑ back to [Olympiad: thinking like a machine, Bebras puzzles ★★★](https://md.mova.elamur.ai/free/en/corpora/questions/ai/31-olympiad-thinking-like-a-machine/)