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 A147621 #12 Oct 24 2022 02:32:53
%S A147621 0,0,0,0,4,26,120,455,1456,4122,10608,25194,55980,117572,235144,
%T A147621 450681,832048,1485800,2575368,4345965,7158060,11532402,18209100,
%U A147621 28224105,43008120,64512240,95365920,139075245,200268432,284997384,401107356
%N A147621 The 3rd Witt transform of A000292.
%C A147621 The 2nd Witt transform is essentially in A032094.
%H A147621 G. C. Greubel, <a href="/A147621/b147621.txt">Table of n, a(n) for n = 0..1000</a>
%H A147621 Pieter Moree, <a href="http://dx.doi.org/10.1016/j.disc.2005.03.004">The formal series Witt transform</a>, Discr. Math. no. 295 vol. 1-3 (2005) 143-160.
%H A147621 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (8,-28,60,-102,168,-258,336,-393,452,-484,452,-393, 336,-258,168,-102,60,-28,8,-1).
%F A147621 G.f.: x^4*(2-x+2*x^2)*(2-2*x+9*x^2-2*x^3+2*x^4)/((1-x)^12*(1+x+x^2)^4).
%F A147621 a(n) = (1/729)*(b(n) + c(n)), where b(n) = n*(n+3)*(n+6)*(3*n^8 +72*n^7 +618*n^6 + 2052*n^5 +207*n^4 -11772*n^3 -14268*n^2 +9648*n -232960)/492800 and c(n) = 9*A049347(n) +5*A049347(n-1) +9*(-1)^n*(A099254(n) -A099254(n-1)) -18(-1)^n*A128504(n) +27*(-1)^n*Sum_{k=0..n} A099254(n-k)*A099254(k-1). - _G. C. Greubel_, Oct 24 2022
%t A147621 CoefficientList[Series[x^4(2*x^2 - x + 2)(2*x^4 - 2*x^3 + 9*x^2 - 2*x+2)/((1-x)^12 * (1 + x + x^2)^4), {x, 0, 40}], x] (* _Vincenzo Librandi_ Dec 13 2012 *)
%o A147621 (Magma) R<x>:=PowerSeriesRing(Integers(), 40); [0,0,0,0] cat Coefficients(R!( x^4*(2-x+2*x^2)*(2-2*x+9*x^2-2*x^3+2*x^4)/((1-x)^12*(1+x+x^2)^4) )); // _G. C. Greubel_, Oct 24 2022
%o A147621 (SageMath)
%o A147621 def A147621_list(prec):
%o A147621 P.<x> = PowerSeriesRing(ZZ, prec)
%o A147621 return P( x^4*(2-x+2*x^2)*(2-2*x+9*x^2-2*x^3+2*x^4)/((1-x)^12*(1+x+x^2)^4) ).list()
%o A147621 A147621_list(40) # _G. C. Greubel_, Oct 24 2022
%Y A147621 Cf. A000292, A032094, A049347, A099254, A128504.
%K A147621 easy,nonn
%O A147621 0,5
%A A147621 _R. J. Mathar_, Nov 08 2008