

A073806


Number of divisors of sum of square of divisors.


1



1, 2, 4, 4, 4, 6, 6, 4, 4, 8, 4, 16, 8, 8, 12, 4, 8, 8, 4, 16, 12, 8, 8, 12, 8, 12, 12, 24, 4, 18, 8, 16, 12, 12, 18, 12, 8, 8, 18, 16, 6, 15, 12, 16, 12, 12, 16, 16, 8, 16, 18, 32, 8, 18, 12, 16, 12, 8, 4, 48, 4, 16, 24, 4, 24, 18, 8, 32, 18, 24, 4, 16, 16, 12, 32, 16, 18, 24, 4, 16, 6
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OFFSET

1,2


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = A000005(A001157(n)) = d(sigma(2, n)).


EXAMPLE

n = 10: D = {1,2,5,10}, sigma(2,10) = 1 + 4 + 25 + 100 = 130, D(130) = {1,2,5,10,13,26,65,130}, so a(10) = 8.


MATHEMATICA

a[n_] := DivisorSigma[0, DivisorSigma[2, n]]; Array[a, 81] (* Amiram Eldar, Aug 01 2019 *)


CROSSREFS

Cf. A000005, A000203, A001157, A062068, A073802A073813.
Sequence in context: A084291 A258573 A060271 * A060849 A130819 A307097
Adjacent sequences: A073803 A073804 A073805 * A073807 A073808 A073809


KEYWORD

nonn


AUTHOR

Labos Elemer, Aug 13 2002


STATUS

approved



