A272229 Numbers n such that n and 3n+1 have the same number of distinct prime divisors.

2, 4, 5, 8, 15, 16, 18, 28, 32, 33, 35, 38, 39, 44, 45, 48, 55, 57, 58, 62, 64, 65, 68, 69, 72, 75, 77, 82, 86, 87, 88, 91, 98, 99, 100, 106, 108, 111, 115, 117, 118, 119, 129, 133, 134, 141, 142, 145, 148, 155, 158, 159, 160, 161, 164, 171, 172, 175, 178, 184, 185, 187, 188, 189

Offset

1,1

Links

G. C. Greubel, Table of n, a(n) for n = 1..2500

Formula

Numbers n such that omega(n) = omega(3n+1).

Maple

with(numtheory): A272229:=n->`if`(nops(factorset(n)) = nops(factorset(3*n+1)), n, NULL): seq(A272229(n), n=1..300); # Wesley Ivan Hurt, Apr 22 2016

Mathematica

Select[Range[500], PrimeNu[#] == PrimeNu[3*# + 1] &] (* G. C. Greubel, May 11 2017 *)

Prog

(PARI) isok(n) = omega(n) == omega(3*n+1); \\ Michel Marcus, Apr 23 2016

Crossrefs

Cf. A001221, A271909.

Sequence in context: A357177 A184775 A240075 * A229083 A194415 A364779

Adjacent sequences: A272226 A272227 A272228 * A272230 A272231 A272232

Keyword

nonn

Author

Benjamin Przybocki, Apr 22 2016

Status

approved