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 A136652 #8 Sep 04 2017 04:12:51 %S A136652 1,3,19,223,4771,190023,14441659,2130394591,616038609331, %T A136652 351153716973303,395928966997611499,885010943452285951183, %U A136652 3928049212346654960720611,34658088824057172975437120103,608435145369338712372672919898779,21266998855813018955669706360248449471 %N A136652 L.g.f.: A(x) = log( Sum_{n>=0} 2^[n(n-1)/2]*x^n ). %H A136652 Vincenzo Librandi, <a href="/A136652/b136652.txt">Table of n, a(n) for n = 1..80</a> %e A136652 L.g.f.: A(x) = x + 3*x^2/2 + 19*x^3/3 + 223*x^4/4 + 4771*x^5/5 +... %e A136652 A(x) = log(1 + x + 2x^2 + 8x^3 + 64x^4 + 1024x^5 +...+ 2^(n(n-1)/2)*x^n +...). %t A136652 max = 14; s = Log[Sum[2^(k*(k-1)/2)*x^k, {k, 0, max}]] + O[x]^(max+1); CoefficientList[s, x]*Range[0, max] // Rest (* _Jean-François Alcover_, Sep 03 2017 *) %o A136652 (PARI) a(n)=n*polcoeff(log(sum(k=0,n,2^(k*(k-1)/2)*x^k +x*O(x^n))),n) %Y A136652 Cf. A136653, A136654. %K A136652 nonn %O A136652 1,2 %A A136652 _Paul D. Hanna_, Jan 15 2008