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 A208061 #14 Mar 03 2014 00:35:19 %S A208061 1,1,1,0,-1,-2,-1,1,4,5,2,-5,-12,-13,-3,17,34,32,-1,-54,-93,-72,28, %T A208061 169,248,152,-147,-510,-646,-282,582,1484,1627,375,-2045,-4195,-3927, %U A208061 110,6716,11544,9002,-3458,-20996,-30921,-19123,17974,63154,80435,35553,-71525,-183969 %N A208061 G.f. 1/sum(k>=0, (-1)^k * x^(k*(k+1)/2)). %F A208061 G.f.: 1 / (1 - x*(1 - x^2*(1 - x^3*(1 - x^4*(1 - ...))))). - _Michael Somos_, Mar 03 2014 %F A208061 Convolution inverse of A197870. - _Michael Somos_, Mar 03 2014 %e A208061 G.f. = 1 + x + x^2 - x^4 - 2*x^5 - x^6 + x^7 + 4*x^8 + 5*x^9 + 2*x^10 - 5*x^11 + ... %o A208061 (PARI) al(n)=Vec(1/(sum(k=0,sqrtint(2*n),(-1)^k*x^(k*(k+1)\2))+x*O(x^n))) %Y A208061 Cf. A006950, A023361, A106507, A197870. %K A208061 sign %O A208061 0,6 %A A208061 _Franklin T. Adams-Watters_, Feb 23 2012