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 A007452 #10 Jul 08 2025 01:00:28 %S A007452 1,-1,0,3,-6,30,0,-630,2520,-22680,0,1247400,-7484400,97297200,0, %T A007452 -10216206000,81729648000,-1389404016000,0,237588086736000, %U A007452 -2375880867360000,49893498214560000,0,-12623055048283680000 %N A007452 Expand cos x / exp x and invert nonzero coefficients. %F A007452 a(4n+2) = 0, a(n) = (-1)^[n == 1, 4, 7 mod 8] * n!/2^floor(n/2). - _Ralf Stephan_, Mar 06 2004 %Y A007452 Absolute values are essentially the same as A046981, where zeros are replaced by ones. %Y A007452 Cf. A052277, A007019, A046979, A007415, A009775, A092820. %K A007452 sign %O A007452 0,4 %A A007452 _N. J. A. Sloane_