A175303 - OEIS

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A175303

a(n) = number of finite sequences using numbers drawn from (1,2,3,...,n), using each number at most once, where each number in a finite sequence is not coprime to the previous number, and each finite sequence must continued if possible. (See example.)

0

1, 2, 3, 4, 5, 13, 14, 43, 79, 457, 458, 5145, 5146, 38237, 259920, 1702869, 1702870, 28603827, 28603828, 402599903, 3319634320, 34246343007, 34246343008

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..23.

FORMULA

a(p)=a(p-1)+1 for all primes p.

EXAMPLE

For n = 7, we have these 14 finite sequences:

1;

2,4,6,3;

2,6,3;

2,6,4;

3,6,2,4;

3,6,4,2;

4,2,6,3;

4,6,2;

4,6,3;

5;

6,2,4;

6,3;

6,4,2;

7

CROSSREFS

Sequence in context: A026471 A039039 A141484 * A057158 A138986 A306294

Adjacent sequences: A175300 A175301 A175302 * A175304 A175305 A175306

KEYWORD

more,nonn

AUTHOR

Leroy Quet, Mar 24 2010

EXTENSIONS

More terms from Sean A. Irvine, Nov 25 2010

STATUS

approved