A130501 a(1)=1, a(n) = number of earlier terms of the sequence that divide (the sum of positive integers which are <=n and missing from first (n-1) terms of sequence).

1, 1, 2, 2, 4, 4, 2, 2, 6, 7, 6, 6, 2, 2, 10, 8, 2, 3, 2, 2, 12, 15, 14, 11, 14, 15, 5, 17, 16, 11, 3, 2, 14, 16, 2, 3, 17, 15, 4, 2, 16, 17, 3, 2, 19, 4, 22, 19, 6, 2, 16, 24, 5, 2, 40, 33, 22, 21, 26, 17, 13, 26, 3, 6, 22, 17, 2, 2, 23, 7, 25, 2, 29, 3, 27, 8, 23, 26, 9, 20

Offset

1,3

Links

Table of n, a(n) for n=1..80.

Example

The positive integers which are <= 9 and are missing from the first 8 terms of the sequence are 3,5,6,7,8,9. The sum of these integers is 38, so a(9) is the number of earlier terms which divide 38. Therefore a(9) = 6.

Mathematica

a = {1}; Do[AppendTo[a, Length[Select[a, Mod[(Plus @@ Complement[Range[n], a]), # ] == 0 &]]], {n, 2, 80}]; a (* Stefan Steinerberger, Dec 26 2007 *)

Crossrefs

Cf. A130500.

Sequence in context: A071928 A325445 A165207 * A049116 A065176 A368558

Adjacent sequences: A130498 A130499 A130500 * A130502 A130503 A130504

Keyword

nonn

Author

Leroy Quet, May 31 2007

Extensions

More terms from Stefan Steinerberger, Dec 26 2007

Status

approved