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 A147990 #5 Jul 14 2016 13:16:56 %S A147990 1,1,-1,1,-3,1,1,-7,13,-7,1,1,-15,83,-220,303,-220,83,-15,1,1,-31,413, %T A147990 -3141,15261,-50187,115410,-189036,222621,-189036,115410,-50187,15261, %U A147990 -3141,413,-31,1,1,-63,1839,-33150,414861,-3841195,27378213,-154299168 %N A147990 Array A147985 (Polynomial coefficients) with zeros deleted. %H A147990 Clark Kimberling, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL12/Kimberling/kimberling56.html">Polynomials associated with reciprocation</a>, JIS 12 (2009) 09.3.4 %F A147990 Let s(1)=x and for n>=2, let s(n)=s(n,x)=S(n,y), where y=x^(1/2) and S(n,x) %F A147990 is as at A147985. Then A147990 gives the coefficients of the polynomials s(n). %e A147990 s(1)=x %e A147990 s(2)=S(2,y)=x-1 %e A147990 s(3)=S(3,y)=x^2-3*x+1 %e A147990 s(4)=S(4,y)=x^4-7*x^3+13*x^2-7*x+1 %e A147990 so that as an array A147990 begins with %e A147990 1 %e A147990 1 -1 %e A147990 1 -3 1 %e A147990 1 -7 13 -7 1 %Y A147990 Cf. A147985, A147986, A147987, A147988, A147989, A147991, A147992, A147993. %K A147990 sign,tabl %O A147990 1,5 %A A147990 _Clark Kimberling_, Nov 25 2008