1,1

Also n+floor(sqrt(5n/2 + 1/2)) since 5n/2 + 1/2 is never a square. [From Charles R Greathouse IV, Feb 11 2011]

Table of n, a(n) for n=1..80.

a=5/2; b=1/2;

Table[n+Floor[(a*n+b)^(1/2)], {n, 80}]

Table[n-1+Ceiling[(n*n-b)/a], {n, 70}]

(PARI) a(n)=n+sqrtint(5*n/2)

Cf. A183863.

Sequence in context: A253723 A014132 A184008 * A254058 A276220 A047381

Adjacent sequences: A183859 A183860 A183861 * A183863 A183864 A183865

nonn,easy

Clark Kimberling, Jan 07 2011

approved