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 A152556 #12 Sep 08 2022 08:45:39 %S A152556 1,2,2,16,20,288,392,8192,11664,320000,468512,15925248,23762752, %T A152556 963780608,1458000000,68719476736,105046700288,5642219814912, %U A152556 8695584276992,524288000000000,813342767698944,54394721876836352,84841494965553152,6232805962420322304 %N A152556 a(n) = 2*(2*n+2)^floor((n-1)/2). %C A152556 Compare to row sums of triangle A152555: 2*(2n+2)^(n-1). %C A152556 Triangle A152555 lists coefficients in a q-analog of the function LambertW(-2x)/(-2x). %H A152556 G. C. Greubel, <a href="/A152556/b152556.txt">Table of n, a(n) for n = 0..640</a> %F A152556 a(n) = Sum_{k=0..n(n-1)/2} A152555(n,k)*(-1)^k. %t A152556 Table[2(2n+2)^Floor[(n-1)/2],{n,0,30}] (* _Harvey P. Dale_, Nov 13 2012 *) %o A152556 (PARI) a(n)=2*(2*n+2)^((n-1)\2) %o A152556 (Magma) [2*(2*n+2)^(Floor((n-1)/2)): n in [0..30]]; // _G. C. Greubel_, Nov 17 2017 %Y A152556 Cf. A152555, A152557(q=2), A152558 (q=3) A152559. %K A152556 nonn %O A152556 0,2 %A A152556 _Paul D. Hanna_, Dec 07 2008