A252891 Numbers n such that sigma(n) is a partition number.

1, 2, 4, 8, 20, 26, 28, 29, 39, 41, 129, 430, 526, 591, 655, 731, 1388, 1622, 2249, 3734, 6841, 18752, 18772, 21332, 35017, 37337, 53173, 105557, 113377, 124753, 419029, 614153, 824149, 829333, 2192923, 2369654, 2538915, 3059853, 3388115, 3479244, 3557183

Offset

1,2

Links

Robert G. Wilson v, Table of n, a(n) for n = 1..65

Example

26 is in the sequence because the sum of divisors of 26 is 1 + 2 + 13 + 26 = 42 and 42 is a partition number because the number of partitions of 10 is equal to 42.

Mathematica

(* To extend the search beyond 50400, be sure to increase the length of partNums accordingly *) partNums = PartionsP[Range[50]]; Select[Range[100], MemberQ[partNums, DivisorSigma[1, #]] &] (* Alonso del Arte, Dec 24 2014 *)

Crossrefs

Cf. A000041, A000203.

Sequence in context: A124154 A296606 A222562 * A102634 A026520 A282983

Adjacent sequences: A252888 A252889 A252890 * A252892 A252893 A252894

Keyword

nonn

Author

Omar E. Pol, Dec 24 2014

Extensions

a(11)-a(16) from Alonso del Arte, Dec 24 2014

More terms from Michel Marcus, Dec 27 2014

Status

approved