A337524 - OEIS

A337524

a(n) = d(n) * (d(n) - 1), where d is the number of divisors of n (A000005).

0, 2, 2, 6, 2, 12, 2, 12, 6, 12, 2, 30, 2, 12, 12, 20, 2, 30, 2, 30, 12, 12, 2, 56, 6, 12, 12, 30, 2, 56, 2, 30, 12, 12, 12, 72, 2, 12, 12, 56, 2, 56, 2, 30, 30, 12, 2, 90, 6, 30, 12, 30, 2, 56, 12, 56, 12, 12, 2, 132, 2, 12, 30, 42, 12, 56, 2, 30, 12, 56, 2, 132, 2, 12, 30, 30

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OFFSET

1,2

COMMENTS

Number of distinct nonsquare m X n matrices such that m and n are divisors of n.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

MATHEMATICA

Table[DivisorSigma[0, n]^2 - DivisorSigma[0, n], {n, 100}]

#(#-1)&/@DivisorSigma[0, Range[100]] (* Harvey P. Dale, Nov 03 2022 *)

CROSSREFS

Cf. A000005 (tau).