login
A280101
a(n) = sigma(sigma(p(n))) = sum of the divisors of the sum of the divisors of number of partitions of n.
1
1, 1, 4, 7, 12, 15, 28, 60, 91, 195, 252, 360, 252, 216, 744, 896, 1020, 1512, 1651, 2400, 3048, 7644, 6552, 4800, 6720, 10890, 24384, 19812, 17360, 20160, 45136, 35280, 40320, 54600, 78624, 68400, 27540, 79248, 115200, 219583, 265980, 200312, 268800, 335160
OFFSET
0,3
LINKS
FORMULA
a(n) = A000203(A139041(n)), n >= 1.
EXAMPLE
For n = 7 the number of partitions of 7 is p(7) = 15, and the sum of the divisors of 15 is sigma(15) = 1 + 3 + 5 + 15 = 24, and the sum of the divisors of 24 is sigma(24) = 1 + 2 + 3 + 4 + 6 + 8 + 12 + 24 = 60, so a(7) = 60.
MATHEMATICA
Array[DivisorSigma[1, DivisorSigma[1, PartitionsP[#]]]&, 43, 0] (* _Amiram Eldar_, Feb 19 2019 *)
PROG
(PARI) a(n) = sigma(sigma(numbpart(n))); \\ _Michel Marcus_, Feb 19 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
_Omar E. Pol_, Dec 25 2016
STATUS
approved