A067291 Numbers n such that prime(n)>n*tau(n) where tau(n) is the number of divisors of n.

1, 5, 7, 11, 13, 17, 19, 23, 25, 29, 31, 33, 34, 35, 37, 38, 39, 41, 43, 46, 47, 49, 51, 53, 55, 57, 58, 59, 61, 62, 65, 67, 69, 71, 73, 74, 77, 79, 81, 82, 83, 85, 86, 87, 89, 91, 93, 94, 95, 97, 101, 103, 106, 107, 109, 111, 113, 115, 118, 119, 121, 122, 123, 125, 127

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Maple

with(numtheory); A067291:=n->`if`(ithprime(n)>n*tau(n), n, NULL); seq(A067291(n), n=1..127); # Wesley Ivan Hurt, Nov 21 2013

Mathematica

Select[Range[200], Prime[#]># DivisorSigma[0, #]&] (* Harvey P. Dale, Jan 13 2020 *)

Prog

(PARI) for(n=1, 161, if(prime(n)>n*numdiv(n), print1(n, ", ")))

Crossrefs

Cf. A000005.

Sequence in context: A306289 A136801 A106571 * A286265 A339911 A007310

Adjacent sequences: A067288 A067289 A067290 * A067292 A067293 A067294

Keyword

nonn

Author

Benoit Cloitre, Feb 24 2002

Status

approved