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 A061138 #4 May 10 2013 12:44:45 %S A061138 0,0,0,0,6,30,90,210,1680,12096,114660,833580,5928120,38112360, %T A061138 259194936,1739195640,17043237120,167089937280,1837707369840, %U A061138 18342985021776,181206905922720,1673742164139360,16992525855006240 %N A061138 Number of degree-n odd permutations of order exactly 4. %F A061138 E.g.f.: - 1/2*exp(x + 1/2*x^2) + 1/2*exp(x - 1/2*x^2) + 1/2*exp(x + 1/2*x^2 + 1/4*x^4) - 1/2*exp(x - 1/2*x^2 - 1/4*x^4). %Y A061138 Cf. A000085, A001470, A001472, A052501, A053496 - A053505, A001189, A001471, A001473, A061121 - A061128, A000704, A061129 - A061132, A048099, A051695, A061133 - A061135, A001465, A061136 - A061140. %K A061138 easy,nonn %O A061138 0,5 %A A061138 _Vladeta Jovovic_, Apr 14 2001