A252891 Numbers m such that sigma(m) 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

Author

Omar E. Pol, Dec 24 2014

Keywords

• nonn

Examples

			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.
		

Links

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

Crossrefs

Cf. A000041, A000203.

Programs

Mathematica

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

Extensions

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

More terms from Michel Marcus, Dec 27 2014