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 A043327 #7 Jul 09 2025 03:50:32 %S A043327 1,1,2,3,6,11,22,43,85,166,327,641,1259,2471,4853,9528,18710,36737, %T A043327 72137,141643,278125,546112,1072322,2105559,4134379,8118070,15940263, %U A043327 31299549,61458328,120676683,236955071,465273846,913589879,1793882179 %N A043327 a(0)=1; a(1)=1; a(n)= a(n-1) + floor( sqrt(a(n-1)*a(n-2))+ sqrt(a(n-3)*a(n-4))+ ... ). %C A043327 Nonlinear recurrence similar to that for Narayana numbers. %t A043327 a[ 0 ]=0; a[ 1 ]=1; a[ n_Integer ] := a[ n ]=a[ n-1 ]+ Floor[ Plus@@Map[ Sqrt[ Times@@# ]&, Partition[ Reverse[ Array[ a, n, 0 ] ], 2 ] ] ] %Y A043327 Cf. A002083, A043328. %K A043327 nonn,easy %O A043327 0,3 %A A043327 _Olivier Gérard_, Jul 18 2001