A110794 a(1)=1, a(n) = Sum_{k=1..n-1} (number of divisors of a(k) that also divide n).

1, 1, 2, 4, 4, 8, 6, 16, 9, 15, 10, 26, 13, 21, 21, 30, 16, 36, 18, 42, 35, 34, 22, 62, 28, 45, 40, 61, 28, 76, 31, 67, 43, 55, 48, 93, 36, 61, 53, 90, 40, 100, 43, 85, 81, 70, 46, 125, 55, 100, 67, 97, 53, 116, 74, 120, 73, 90, 58, 183, 63, 98, 104, 127, 84, 136, 68, 135, 90

Offset

1,3

Links

Table of n, a(n) for n=1..69.

Example

The divisors of the first 5 terms of the sequence are a(1):1; a(2):1; a(3):1,2; a(4):1,2,4; a(5):1,2,4. Eight of these divisors divide 6. (These divisors are 1;1;1,2;1,2;1,2.) So a(6) = 8.

Mathematica

a = {1}; Do[AppendTo[a, Sum[Length[Select[Divisors[a[[i]]], Mod[Length[a] + 1, # ] == 0 &]], {i, 1, Length[a]}]], {70}]; a (* Stefan Steinerberger, Oct 16 2007 *)

Crossrefs

Sequence in context: A329718 A077764 A366621 * A117295 A235999 A093820

Adjacent sequences: A110791 A110792 A110793 * A110795 A110796 A110797

Keyword

nonn

Author

Leroy Quet, Apr 26 2007

Extensions

More terms from Stefan Steinerberger, Oct 16 2007

Status

approved