login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
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
Sequence in context: A111234 A117248 A343292 * A146288 A244361 A199424
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 04:58 EDT 2024. Contains 371235 sequences. (Running on oeis4.)