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 A083090 #8 Jun 23 2019 02:27:31 %S A083090 1,5,25,90,247,766,2258,5860,16526,45639,124043,313327,837221,2216256, %T A083090 5545541,14524810,37810204,97907017,242993558,625252309,1602714963, %U A083090 3962518559,10109705767,25718726896,63402237401,160711911464 %N A083090 Main diagonal of table A083087. %F A083090 a(n) = T(n, n), where T(n, 0) = floor(n*x/(x-1)) + 1, T(n, k+1) = ceiling(x*T(n, k)), for n >= 0, k >= 0, where x = 1+sqrt(2). %Y A083090 Cf. A083087, A083044, A083047, A083050. %K A083090 nonn %O A083090 0,2 %A A083090 _Paul D. Hanna_, Apr 22 2003