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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Daniel Suteu, Table of n, a(n) for n = 0..3000

FORMULA

a(n) = A000203(A000203(A000041(n))) = A051027(A000041(n)).

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

Cf. A000041, A000203, A051027, A139041.

Sequence in context: A075624 A008333 A076295 * A310779 A083030 A310780

Adjacent sequences:  A280098 A280099 A280100 * A280102 A280103 A280104

KEYWORD

nonn

AUTHOR

Omar E. Pol, Dec 25 2016

STATUS

approved

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Last modified August 6 15:23 EDT 2020. Contains 336248 sequences. (Running on oeis4.)