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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 (list; graph; refs; listen; history; text; internal format)
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, A073802-A073813.

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

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Last modified June 6 11:14 EDT 2020. Contains 334827 sequences. (Running on oeis4.)