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A374915
a(n) = (n - 1) * (n - 2) * sigma(n).
0
0, 0, 8, 42, 72, 240, 240, 630, 728, 1296, 1080, 3080, 1848, 3744, 4368, 6510, 4320, 10608, 6120, 14364, 12160, 15120, 11088, 30360, 17112, 25200, 26000, 39312, 22680, 58464, 27840, 58590, 47616, 57024, 53856, 108290, 47880, 79920, 78736, 133380, 65520, 157440
OFFSET
1,3
LINKS
William Craig, Jan-Willem van Ittersum, and Ken Ono, Integer partitions detect the primes, arXiv:2405.06451v2 [math.CO], Jul 10 2024.
FORMULA
a(n) = A002378(n-2) * A000203(n).
a(n) >= 8 * A002127(n) and the equal sign only holds if n is 1 or prime.
MATHEMATICA
a[n_]:= (n - 1) * (n - 2) * DivisorSigma[1, n]; Array[a, 42] (* Stefano Spezia, Jul 23 2024 *)
PROG
(PARI) a(n) = (n-1)*(n-2)*sigma(n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 23 2024
STATUS
approved