login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A067290 Numbers n such that prime(n)<n*tau(n) where tau(n) is the number of divisors of n. 1
2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 26, 27, 28, 30, 32, 36, 40, 42, 44, 45, 48, 50, 52, 54, 56, 60, 63, 64, 66, 68, 70, 72, 75, 76, 78, 80, 84, 88, 90, 92, 96, 98, 99, 100, 102, 104, 105, 108, 110, 112, 114, 116, 117, 120, 124, 126, 128, 130, 132 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Visible sharp bends on the graph around the 500th and 15000th terms occur where the ratio prime(n)/n exceeds 8 and 12, correspondingly. - Ivan Neretin, Oct 16 2016

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..20000

MATHEMATICA

Select[Range@135, Prime[#] < #*DivisorSigma[0, #] &] (* Ivan Neretin, Oct 16 2016 *)

PROG

(PARI) for(n=1, 171, if(prime(n)<n*numdiv(n), print1(n, ", ")))

CROSSREFS

Cf. A000005.

Sequence in context: A063450 A047229 A094229 * A106577 A068577 A225731

Adjacent sequences:  A067287 A067288 A067289 * A067291 A067292 A067293

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Feb 24 2002

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 13 12:45 EST 2019. Contains 329094 sequences. (Running on oeis4.)