|
%I #9 Oct 02 2021 14:59:27
%S 0,0,1,1,1,2,2,2,2,3,3,3,3,3,4,4,4,4,4,4,5,5,5,5,5,5,5,6,6,6,6,6,6,6,
%T 6,7,7,7,7,7,7,7,7,7,8,8,8,8,8,8,8,8,8,8,9,9,9,9,9,9,9,9,9,9,9,10,10,
%U 10,10,10,10,10,10,10,10,10,10,11,11,11,11,11,11,11
%N a(n) = floor((sqrt(1+8*n)-3)/2).
%D R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 7.2(d).
%t Floor[(Sqrt[1 + 8 Range[100]] - 3)/2] (* _Wesley Ivan Hurt_, Oct 02 2021 *)
%K nonn
%O 1,6
%A _N. J. A. Sloane_, Jan 23 2000
|
