A156122 - OEIS

%I #7 Sep 28 2018 19:16:26

%S 1,6,192,15216,2249472,534437376,186227300352,89472023771136,

%T 56685374949752832,45789401925385322496,45932606279820521766912,

%U 56019030070478949980307456,81629508898089483953705582592,140066108036622450865749167702016,279529326198310211796977967402319872

%N a(n) = P_{2n}(sqrt(2))/sqrt(2) (see A155100).

%H G. C. Greubel, <a href="/A156122/b156122.txt">Table of n, a(n) for n = 0..207</a>

%t 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 Cf. A155100.

%K nonn

%O 0,2

%A _N. J. A. Sloane_, Nov 05 2009