A186444 The count of numbers <= n for which 3 is an infinitary divisor.

0, 0, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 11, 11, 11, 11, 11, 11, 12, 12, 12, 13, 13, 13, 14, 14, 14, 15, 15, 15, 16, 16, 16, 16, 16, 16, 17, 17, 17, 18, 18, 18, 18, 18, 18, 19

Offset

1,6

Comments

For the definition of infinitary divisors, see A037445.

The sequence is the partial sums of the characteristic function of the numbers with 3 as one of the infinitary divisors; these are 3, 6, 12, 15, 21, 24, 27, 30 etc, apparently shown in A145204. - R. J. Mathar, Feb 28 2011

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = floor(n/3) - a(floor(n/3)).

a(n) = floor(n/3) - floor(n/9) + floor(n/27) - ....

a(n) grows as n/4 as n tends to infinity.

Maple

A186444 := proc(n) local a, k ; option remember; if n< 3 then 0; else floor(n/3) -procname(floor(n/3)) ; end if; end proc: # R. J. Mathar, Feb 28 2011

Crossrefs

Cf. A123087, A037445.

Partial sums of A182581.

Sequence in context: A235122 A131996 A090618 * A072748 A174631 A278949

Adjacent sequences: A186441 A186442 A186443 * A186445 A186446 A186447

Keyword

nonn

Author

Vladimir Shevelev, Feb 21 2011

Status

approved