A122206 Number of sequences b with last index n with b(0) = 1, b(i+1) = b(i)+d where d|b(i).

1, 1, 2, 5, 17, 66, 307, 1619, 9668, 64112, 469936, 3773496, 32997159, 312542002, 3192352420, 35023164817, 411288004670, 5154265796088, 68746349160704, 973526723323087, 14605620692012861, 231694886107899371

Offset

0,3

Comments

b(n) can be as large as 2^n. [From Max Alekseyev, May 10 2009]

Links

Table of n, a(n) for n=0..21.

Example

For n=3, the sequences are 1,2,3,4; 1,2,3,6; 1,2,4,5; 1,2,4,6; and 1,2,4,8. We can't have 1,2,3,5 because the difference (5-3) does not divide 3.

Crossrefs

Cf. A117497, A122205.

Sequence in context: A346506 A362967 A062881 * A104082 A166474 A054769

Adjacent sequences: A122203 A122204 A122205 * A122207 A122208 A122209

Keyword

nonn

Author

Franklin T. Adams-Watters, Aug 25 2006

Extensions

a(15)..a(21) from Max Alekseyev, May 10 2009

Status

approved