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A337524
a(n) = d(n) * (d(n) - 1), where d is the number of divisors of n (A000005).
1
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
OFFSET
1,2
COMMENTS
Number of distinct nonsquare m X n matrices such that m and n are divisors of n.
LINKS
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).
Equals twice A066446.
Sequence in context: A176991 A264666 A283362 * A324047 A091818 A324202
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Aug 30 2020
STATUS
approved