

A079788


a(n) = count of numbers <= n for which the number of divisors is also <= tau(n).


2



1, 2, 3, 4, 4, 6, 5, 8, 7, 10, 6, 12, 7, 13, 14, 15, 8, 18, 9, 20, 17, 18, 10, 24, 13, 21, 22, 27, 11, 30, 12, 30, 25, 26, 27, 36, 13, 29, 30, 39, 14, 41, 15, 39, 40, 33, 16, 48, 20, 44, 36, 46, 17, 52, 38, 54, 39, 40, 18, 60, 19, 43, 54, 55, 44, 63, 20, 57, 46, 67, 21, 72, 22, 49
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..74.


EXAMPLE

a(7) = 5 as 1, 2, 3, 5 and 7 qualify for the count.


MATHEMATICA

Do[s = 0; For[i = 1, i <= n, i++, If[DivisorSigma[0, i] <= DivisorSigma[0, n], s++ ]]; Print[s], {n, 1, 50}]  Ryan Propper, Mar 30 2006


PROG

(PARI) for(n=1, 200, m=0; sn=sigma(n, 0); for(i = 1, n, if(sigma(i, 0)<=sn, m++)); print1(m", "))  Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007


CROSSREFS

Cf. A138009, A067004.
Sequence in context: A071324 A063655 A117248 * A146288 A244361 A199424
Adjacent sequences: A079785 A079786 A079787 * A079789 A079790 A079791


KEYWORD

nonn


AUTHOR

Amarnath Murthy, Feb 03 2003


EXTENSIONS

More terms from Ryan Propper, Mar 30 2006
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Apr 28 2007


STATUS

approved



