login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A067930 Nonprime solutions to k == -1 (mod phi(k+1)). 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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 24 05:38 EDT 2021. Contains 348217 sequences. (Running on oeis4.)