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 A033690 #18 Nov 04 2015 03:46:55 %S A033690 1,4,14,28,57,84,148,196,312,364,546,624,910,988,1352,1456,1974,2072, %T A033690 2710,2800,3705,3724,4816,4788,6188,6076,7658,7644,9620,9352,11536, %U A033690 11284,14183,13468,16542,15996,19864,18928,22820,21904,26880,25284 %N A033690 Theta series of A2[hole]^4. %D A033690 J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 111, Eq (63)^4. %F A033690 a(n) = A033685^4. %F A033690 Expansion of q^(-4/3) * (eta(q^3)^3 / eta(q))^4 in powers of q. - _Michael Somos_, Aug 22 2007 %F A033690 Expansion of c(q)^4 / (81 * q^(4/3)) in powers of q where c() is a cubic AGM function. - _Michael Somos_, Aug 22 2007 %F A033690 Euler transform of period 3 sequence [ 4, 4, -8, ...]. - _Michael Somos_, Aug 22 2007 %F A033690 A092342(n) = A000731(n) + 81*a(n-1). - _Michael Somos_, Aug 22 2007 %e A033690 q^4 + 4*q^7 + 14*q^10 + 28*q^13 + 57*q^16 + 84*q^19 + 148*q^22 + ... %t A033690 s = (QPochhammer[q^3]^3/QPochhammer[q])^4 + O[q]^45; CoefficientList[s, q] (* _Jean-François Alcover_, Nov 04 2015 *) %o A033690 (PARI) {a(n) = local(A); if(n<0, 0, A = x*O(x^n); polcoeff( (eta(x^3 +A)^3 / eta(x +A) )^4, n))} /* _Michael Somos_, Aug 22 2007 */ %Y A033690 Cf. A033685. %K A033690 nonn %O A033690 0,2 %A A033690 _N. J. A. Sloane_