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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
OFFSET
1,2
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
KEYWORD
more,nonn
AUTHOR
Leroy Quet, Mar 24 2010
EXTENSIONS
More terms from Sean A. Irvine, Nov 25 2010
STATUS
approved