

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(p1)+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 A098552
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



