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A062835 a(1) = 0; for n > 1 a(n) = sum of divisors of n^2-1; or sigma(A005563(n-1)).

%I A062835 #33 Dec 09 2024 05:28:49
%S A062835 0,4,15,24,60,48,124,104,186,156,360,168,480,336,504,432,819,360,1170,
%T A062835 640,1080,768,1488,744,1736,1240,1680,1200,2880,960,3048,1536,2286,
%U A062835 2304,3510,1824,3900,2128,3720,2352,5952,1848,5760,3432,4320,3744,6048
%N A062835 a(1) = 0; for n > 1 a(n) = sum of divisors of n^2-1; or sigma(A005563(n-1)).
%H A062835 Metin Sariyar, <a href="/A062835/b062835.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harry J. Smith)
%F A062835 Sum_{k=1..n} a(k) = (35/48) * n^3 + O((n*log(n))^2). - _Amiram Eldar_, Dec 09 2024
%p A062835 with(numtheory): seq( `if`(n=1, 0, sigma(n^2 -1)), n=1..100); # _G. C. Greubel_, Dec 31 2019
%t A062835 Table[If[n==1,0,DivisorSigma[1, n^2 - 1]], {n, 120}] (* corrected by _Metin Sariyar_, Dec 12 2019 *)
%o A062835 (PARI) a(n)={if(n<2, 0, sigma(n^2 - 1))}
%o A062835 (Magma) [0] cat [DivisorSigma(1, n^2 -1): n in [2..100]]; // _G. C. Greubel_, Dec 31 2019
%o A062835 (Sage) [0]+[sigma(n^2 -1, 1) for n in (2..100)] # _G. C. Greubel_, Dec 31 2019
%o A062835 (GAP) Concatenation([0], List([2..100], n-> Sigma(n^2 -1) )); # _G. C. Greubel_, Dec 31 2019
%Y A062835 Cf. A000203, A005563.
%K A062835 easy,nonn
%O A062835 1,2
%A A062835 _Jason Earls_, Jul 21 2001
%E A062835 Name corrected by _Omar E. Pol_, Dec 08 2019