A068993 Numbers k such that A062799(k) = 4.

6, 10, 14, 15, 16, 21, 22, 26, 33, 34, 35, 38, 39, 46, 51, 55, 57, 58, 62, 65, 69, 74, 77, 81, 82, 85, 86, 87, 91, 93, 94, 95, 106, 111, 115, 118, 119, 122, 123, 129, 133, 134, 141, 142, 143, 145, 146, 155, 158, 159, 161, 166, 177, 178, 183, 185, 187, 194, 201

Offset

1,1

Comments

4*a(n)^2 are the solutions to A048272(x) = -Sum_{d|x} (-1)^d = -9 - Benoit Cloitre, Apr 14 2002

Links

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

Formula

A113901(a(n)) = 4. - Reinhard Zumkeller, Mar 13 2011

Mathematica

f[n_] := DivisorSum[n, PrimeNu[#] &]; Select[Range[201], f[#] == 4 &] (* Amiram Eldar, Jul 25 2020 *)

Prog

(PARI) for(n=1, 100, if(sumdiv(n, d, omega(d))==4, print1(n, ", ")))
(PARI) is(n)=my(f=factor(n)[, 2]~); f==[1, 1] || f==[4] \\ Charles R Greathouse IV, Oct 15 2015

Crossrefs

Union of A006881 and A030514.

Cf. A048272, A062799, A113901.

Sequence in context: A315158 A315159 A063774 * A138592 A357850 A085232

Adjacent sequences: A068990 A068991 A068992 * A068994 A068995 A068996

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 06 2002

Status

approved