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 A101634 #6 Dec 28 2021 17:28:12
%S A101634 6,5,6,9,20,75,414,2849,22728,204471,2044610,22490589,269886924,
%T A101634 3508529843,49119417606,736791263865,11788660221584,200407223766639,
%U A101634 3607330027799178,68539270528184021,1370785410563680020
%N A101634 Subtract 1, multiply by 1, subtract 2, multiply by 2, etc.
%C A101634 Inspired by A019460. a(1) = 6 is the least integer producing all nonnegative terms.
%F A101634 Recurrence: a(1) = 6; a(n+1) = n*a(n) - n^2. [Edited by _Georg Fischer_, Dec 28 2021]
%t A101634 a=6;bb={a};Do[b=i(a-i);a=b;bb={bb, a}, {i, 20}];Flatten[bb]
%Y A101634 Cf. A019460.
%K A101634 easy,nonn
%O A101634 1,1
%A A101634 _Zak Seidov_, Jan 26 2005