This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A143337 #6 Apr 07 2015 21:06:54 %S A143337 1,24,-72,96,-168,144,-288,192,-360,312,-432,288,-672,336,-576,576, %T A143337 -744,432,-936,480,-1008,768,-864,576,-1440,744,-1008,960,-1344,720, %U A143337 -1728,768,-1512,1152,-1296,1152,-2184,912,-1440,1344,-2160,1008,-2304,1056,-2016,1872,-1728,1152 %N A143337 Expansion of K(k) * (6 * E(k) - (1 + 4*k'^2) * K(k)) / (Pi/2)^2 in powers of q where E(k), K(k) are complete elliptic integrals and q = exp(-Pi * K(k') / K(k)). %F A143337 G.f.: 1 - 24 * Sum_{k>0} k * (-x)^k / (1 - (-x)^k) = 1 - 24 * Sum_{k>0} (-x)^k / (1 - (-x)^k)^2. %F A143337 a(n) = (-1)^n * A006352(n). %F A143337 a(n) = 24 * A143348(n) unless n=0. %F A143337 Expansion of -(P(q) - 6 * P(q^2) + 4 * P(q^4)) in powers of q where P() is a Ramanujan Lambert series. - _Michael Somos_, Apr 07 2015 %e A143337 G.f. = 1 + 24*q - 72*q^2 + 96*q^3 - 168*q^4 + 144*q^5 - 288*q^6 + 192*q^7 + ... %t A143337 a[ n_] := If[ n < 1, Boole[n == 0], -(-1)^n 24 DivisorSigma[ 1, n]]; (* _Michael Somos_, Apr 07 2015 *) %o A143337 (PARI) {a(n) = if( n<1, n==0, -(-1)^n * 24 * sigma(n))}; %Y A143337 Cf. A006352, A143348. %K A143337 sign %O A143337 0,2 %A A143337 _Michael Somos_, Aug 09 2008