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 A156122 #7 Sep 28 2018 19:16:26
%S A156122 1,6,192,15216,2249472,534437376,186227300352,89472023771136,
%T A156122 56685374949752832,45789401925385322496,45932606279820521766912,
%U A156122 56019030070478949980307456,81629508898089483953705582592,140066108036622450865749167702016,279529326198310211796977967402319872
%N A156122 a(n) = P_{2n}(sqrt(2))/sqrt(2) (see A155100).
%H A156122 G. C. Greubel, <a href="/A156122/b156122.txt">Table of n, a(n) for n = 0..207</a>
%t A156122 p[n_, u_]:= D[Tan[x], {x, n}] /. Tan[x] -> u /. Sec[x] -> Sqrt[1 + u^2] // Expand; p[-1, u_] = 1; Table[p[n, Sqrt[2]]/Sqrt[2], {n, -1, 100}][[2 ;; ;; 2]] (* _G. C. Greubel_, Sep 28 2018 *)
%Y A156122 Cf. A155100.
%K A156122 nonn
%O A156122 0,2
%A A156122 _N. J. A. Sloane_, Nov 05 2009