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 A082428 #20 Apr 27 2025 11:51:02
%S A082428 1,5,21,111,693,4989,40743,372507,3771633,41907033,507075099,
%T A082428 6638074023,93486209157,1409484384213,22652427603423,386601431098419,
%U A082428 6982988349215193,133087542655630737,2669144605482372003,56192518010155200063,1239045022123922161389,28557037652760872672013
%N A082428 a(1) = 1; a(n) = 3 + n * Sum_{k=1..n-1} a(k).
%F A082428 for n>=2 a(n) = ceiling(n*(3e-7)*n!).
%F A082428 From _Seiichi Manyama_, Apr 27 2025: (Start)
%F A082428 E.g.f.: -3 - x + (-7*x + 3*exp(x))/(1-x)^2.
%F A082428 a(n) = -7 * n * n! + 3 * Sum_{k=0..n} (k+1)! * binomial(n,k) for n > 1.
%F A082428 a(n) = (n^2 * a(n-1) - 3)/(n-1) for n > 2.
%F A082428 a(n) = (n+2) * a(n-1) - (n-1) * a(n-2) for n > 3. (End)
%Y A082428 Cf. A007808, A074143, A082425, A082427, A082430, A383436, A383437.
%Y A082428 Cf. A001339.
%K A082428 nonn
%O A082428 1,2
%A A082428 _Benoit Cloitre_, Apr 24 2003