A083539 a(n) = sigma(n) * sigma(n+1): product of sigma-values for consecutive integers.

3, 12, 28, 42, 72, 96, 120, 195, 234, 216, 336, 392, 336, 576, 744, 558, 702, 780, 840, 1344, 1152, 864, 1440, 1860, 1302, 1680, 2240, 1680, 2160, 2304, 2016, 3024, 2592, 2592, 4368, 3458, 2280, 3360, 5040, 3780, 4032, 4224, 3696, 6552, 5616, 3456, 5952

Offset: 1

Author

Labos Elemer, May 21 2003

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A000203, A002378, A060781, A060780, A083538, A330322 (partial sums).

Cf. A083481, A083542, A092517.

Programs

Mathematica

f[x_] := DivisorSigma[1, x]; t=Table[f[w+1]*f[w], {w, 1, 128}]
Times@@@Partition[DivisorSigma[1,Range[50]],2,1] (* Harvey P. Dale, May 21 2014 *)

PARI

a(n)=sigma(n)*sigma(n+1) \\ Charles R Greathouse IV, Feb 14 2013

Formula

a(n) = A000203(A002378(n)). - Amiram Eldar, Jul 10 2024