OFFSET
0,3
LINKS
Daniel Suteu, Table of n, a(n) for n = 0..3000
FORMULA
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