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 A308645 #5 Jun 13 2019 12:54:13
%S A308645 1,-1,-3,3,41,87,-571,-5701,-14575,156655,2094925,9148851,-63364423,
%T A308645 -1474212665,-11494853995,10945362411,1520718442785,20719421344991,
%U A308645 100137575499165,-1638818071763869,-45333849658449847,-512404024891840969,-577060092568365467,99142586163648127771
%N A308645 Expansion of e.g.f. exp(1 + x - exp(2*x)).
%F A308645 a(n) = exp(1) * Sum_{k>=0} (-1)^k*(2*k + 1)^n/k!.
%F A308645 a(n) = Sum_{k=0..n} binomial(n,k)*2^k*A000587(k).
%t A308645 nmax = 23; CoefficientList[Series[Exp[1 + x - Exp[2 x]], {x, 0, nmax}], x] Range[0, nmax]!
%t A308645 Table[Exp[1] Sum[(-1)^k (2 k + 1)^n/k!, {k, 0, Infinity}], {n, 0, 23}]
%t A308645 Table[Sum[Binomial[n, k] 2^k BellB[k, -1], {k, 0, n}], {n, 0, 23}]
%Y A308645 Cf. A000587, A055882, A126390, A308536.
%K A308645 sign
%O A308645 0,3
%A A308645 _Ilya Gutkovskiy_, Jun 13 2019