A066377 Number of numbers m <= n such that floor(sqrt(m)) divides m.

1, 3, 6, 10, 16, 24, 33, 45, 60, 76, 96, 120, 145, 175, 210, 246, 288, 336, 385, 441, 504, 568, 640, 720, 801, 891, 990, 1090, 1200, 1320, 1441, 1573, 1716, 1860, 2016, 2184, 2353, 2535, 2730, 2926, 3136, 3360, 3585, 3825, 4080, 4336

Offset: 1

Author

N. J. A. Sloane, Dec 23 2001

Keywords

• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000
• Index entries for linear recurrences with constant coefficients, signature (2,-1,2,-4,2,-1,2,-1).

Crossrefs

Partial sums of A006446.

Programs

PARI

{ n=0; a=0; for (m=1, 10^9, if (m%floor(sqrt(m)) == 0, a+=m; write("b066377.txt", n++, " ", a); if (n==1000, return)) ) } \\ Harry J. Smith, Feb 12 2010

Formula

G.f.: -x*(x^3-x^2-x-1) / ((x-1)^4*(x^2+x+1)^2). - Colin Barker, Jan 12 2013