OFFSET
0,8
FORMULA
From Ridouane Oudra, May 11 2019: (Start)
a(n) = (1/2)*(n + 1 - t - abs(n + 1 - t^2)), where t = floor(sqrt(n+1) + 1/2).
PROG
(Magma) [1/2*(n+1-Floor(Sqrt(n+1)+1/2)-Abs(n+1-(Floor(Sqrt(n+1)+1/2))^2)):n in [0..90]]; // Marius A. Burtea, May 09 2019
(PARI) f(n) = sqrtint(4*n)-2*sqrtint(n); \\ A023969
a(n) = sum(k=0, n, f(k)); \\ Michel Marcus, May 10 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 20 2003
STATUS
approved