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 A026021 #7 Apr 10 2022 14:27:14 %S A026021 1,1,2,3,6,10,19,34,62,117,207,407,704,1430,2431,5070,8502,18122, %T A026021 30056,65246,107236,236436,385662,861764,1396652,3157325,5088865, %U A026021 11622015,18642420,42961470,68624295,159419670,253706790,593636670,941630580 %N A026021 T(n,[ n/2 ]), where T is the array defined in A026009. %F A026021 Conjecture: -(n+7)*(5*n-34)*a(n) +8*(-n-14)*a(n-1) +(27*n^2-83*n-428)*a(n-2) +8*(4*n+5)*a(n-3) 44*(n-3)*(7*n-27)*a(n-4)=0. - _R. J. Mathar_, Jun 20 2013 %Y A026021 Cf. A026009. %K A026021 nonn %O A026021 0,3 %A A026021 _Clark Kimberling_