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 A083091 #7 Dec 02 2016 01:13:46
%S A083091 1,5,17,49,128,321,790,1924,4664,11282,27262,65843,158988,383863,
%T A083091 926761,2237435,5401685,13040863,31483472,76007871,183499282,
%U A083091 443006506,1069512368,2582031320,6233575089,15049181582,36331938341,87713058356
%N A083091 Antidiagonal sums of table A083087.
%F A083091 a(n) = Sum_{k=0..n} T(k, n-k), where T(n, 0) = floor(n*x/(x-1)) + 1, T(n, k+1) = ceiling(x*T(n, k)), for n>=0, k>=0, with x = 1 + sqrt(2).
%Y A083091 Cf. A083087, A083044, A083047, A083050.
%K A083091 nonn
%O A083091 0,2
%A A083091 _Paul D. Hanna_, Apr 22 2003