A071388 Card[InvPhi(n)] is a prime number.

1, 2, 8, 10, 20, 22, 28, 30, 32, 44, 46, 48, 52, 54, 56, 58, 66, 70, 72, 78, 82, 92, 96, 102, 104, 106, 110, 116, 120, 126, 130, 132, 136, 138, 140, 148, 150, 156, 164, 166, 172, 178, 190, 196, 198, 204, 210, 212, 216, 220, 222, 226, 228, 238, 240, 250, 260, 262

Offset

1,2

Comments

All terms except 1 are even. - Robert Israel, Mar 29 2020

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

InvPhi[48]={65,104,105,112,130,140,144,156,168,180,210} has 11 terms, so 48 is here.

Maple

filter:= n -> isprime(nops(numtheory:-invphi(n))):
select(filter, [$1..400]); # Robert Israel, Mar 29 2020

Crossrefs

Cf. A000010, A007366, A007367, A014197, A058277, A060668, A060670, A060674, A063512, A071386-A071389.

Sequence in context: A294157 A082396 A195582 * A209202 A032356 A114272

Adjacent sequences: A071385 A071386 A071387 * A071389 A071390 A071391

Keyword

nonn

Author

Labos Elemer, May 23 2002

Status

approved