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 A170930 #4 Jun 02 2025 02:13:10 %S A170930 0,21,63,252,945,3591,13608,51597,195615,741636,2811753,10660167, %T A170930 40415760,153227781,580930623,2202475212,8350217505,31658078151, %U A170930 120024886968,455048895357,1725221346975,6540810726996,24798096221913 %N A170930 G(n,1) with n index G(n,i)=n*(G(n,i-1)+G(n,i-2))=(a^i-b^i)*d where d=sqrt(n*(n+4)); a=(n+d)/2; b=(n-d)/2. %C A170930 n=1 A022088 n=2 12*A002605 n=3 above n=4 ... new %F A170930 a(n) = 3*a(n-1)+3*a(n-2) = 21*A030195(n). G.f.: 21*x/(1-3*x-3*x^2). [From _R. J. Mathar_, Feb 05 2010] %e A170930 G(n,0)=0 G(n,1)=n*(n+4) %Y A170930 see above %K A170930 nonn %O A170930 0,2 %A A170930 Claudio Peruzzi (claudio.peruzzi(AT)gmail.com), Feb 04 2010 %E A170930 More terms from _R. J. Mathar_, Feb 05 2010