A083539 - OEIS

%I #20 Jul 10 2024 02:57:51

%S 3,12,28,42,72,96,120,195,234,216,336,392,336,576,744,558,702,780,840,

%T 1344,1152,864,1440,1860,1302,1680,2240,1680,2160,2304,2016,3024,2592,

%U 2592,4368,3458,2280,3360,5040,3780,4032,4224,3696,6552,5616,3456,5952

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

%H Harvey P. Dale, <a href="/A083539/b083539.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = A000203(A002378(n)). - _Amiram Eldar_, Jul 10 2024

%t f[x_] := DivisorSigma[1, x]; t=Table[f[w+1]*f[w], {w, 1, 128}]

%t Times@@@Partition[DivisorSigma[1,Range[50]],2,1] (* _Harvey P. Dale_, May 21 2014 *)

%o (PARI) a(n)=sigma(n)*sigma(n+1) \\ _Charles R Greathouse IV_, Feb 14 2013

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

%Y Cf. A083481, A083542, A092517.

%K nonn,easy

%O 1,1

%A _Labos Elemer_, May 21 2003