A063038 a(n) = floor(n*sqrt(n)) - d(n), where d(n) is the number of divisors function.

0, 0, 3, 5, 9, 10, 16, 18, 24, 27, 34, 35, 44, 48, 54, 59, 68, 70, 80, 83, 92, 99, 108, 109, 122, 128, 136, 142, 154, 156, 170, 175, 185, 194, 203, 207, 223, 230, 239, 244, 260, 264, 279, 285, 295, 307, 320, 322, 340, 347, 360, 368, 383, 388, 403, 411, 426, 437

Offset: 1

Author

Jason Earls, Aug 03 2001

Keywords

• easy
• nonn

Crossrefs

Cf. A000005, A000093, A055682.

Programs

Mathematica

Table[Floor[n*Sqrt[n]] - DivisorSigma[0, n], {n, 50}] (* Wesley Ivan Hurt, Jun 09 2014 *)

PARI

j=[]; for(n=1,100,j=concat(j,floor(n*sqrt(n))-numdiv(n))); j

Formula

a(n) = A000093(n) - A000005(n). - Michel Marcus, Apr 13 2024