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 A371683 #13 Apr 06 2024 14:58:15
%S A371683 1,3,33,819,37281,2720643,291107457,42945429747,8354465297601,
%T A371683 2072193715976067,638269648981638753,239021193599722872627,
%U A371683 106946291677392350660961,56346809266835212819000323,34528790475992735166895973313,24349545528533035663737512791539
%N A371683 a(n) = Sum_{k=0..n} (-2)^(3*k)*binomial(2*n, 2*k)*Euler(2*k, 1/2). Row sums of A371637.
%F A371683 a(n) ~ cosh(Pi/(2*sqrt(2))) * 2^(5*n+3) * n^(2*n + 1/2) / (Pi^(2*n + 1/2) * exp(2*n)). - _Vaclav Kotesovec_, Apr 03 2024
%p A371683 seq(add((-8)^k*binomial(2*n, 2*k)*euler(2*k, 1/2), k = 0..n), n = 0..15);
%t A371683 Table[Sum[(-2)^(3*k)*Binomial[2*n,2*k]*EulerE[2*k,1/2],{k,0,n}],{n,0,15}] (* _James C. McMahon_, Apr 05 2024 *)
%Y A371683 Cf. A371637, A371684.
%K A371683 nonn
%O A371683 0,2
%A A371683 _Peter Luschny_, Apr 03 2024