A067930 Nonprime solutions to k == -1 (mod phi(k+1)).

1, 15, 35, 63, 95, 143, 161, 215, 255, 287, 323, 485, 511, 575, 767, 1023, 1295, 1457, 1535, 1727, 1943, 2047, 2303, 2915, 3071, 3455, 3887, 4095, 4607, 5183, 5831, 7775, 9215, 10367, 11663, 12287, 13823, 16383, 17495, 18431, 20735, 24575, 26243, 31103, 32767

Offset

1,2

Comments

Odd terms in A005105 are primes solutions to p==-1 (mod phi(p+1)).

Links

Amiram Eldar, Table of n, a(n) for n = 1..336 (terms below 5*10^10)

Mathematica

Select[Range[30000], !PrimeQ[#] && Divisible[# + 1, EulerPhi[# + 1]] &] (* Amiram Eldar, Nov 29 2020 *)

Prog

(PARI) isok(m) = !isprime(m) && (Mod(m, eulerphi(m+1)) == -1); \\ Michel Marcus, Nov 29 2020

Crossrefs

Cf. A000010, A005105.

Sequence in context: A340449 A063532 A212331 * A257836 A146688 A146656

Adjacent sequences: A067927 A067928 A067929 * A067931 A067932 A067933

Keyword

nonn

Author

Benoit Cloitre, Feb 22 2002

Status

approved