OFFSET
1,1
COMMENTS
The first 962 terms, all those with n<500000, are also in A023228. - R. J. Mathar, Oct 20 2006
All terms are in A023228, i.e., such that 8p+1 is prime, since a divisor of 8p+1 would also divide M(p)=A000225(p) and thus be of the form 2kp+1, but it is easily checked that 8p+1 cannot be a multiple of 2p+1 (nor of 4p+1 or 6p+1, of course). - M. F. Hasler, Mar 21 2011
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
29 is in this sequence because 2^29-1 is divisible by 8 * 29 + 1 = 233.
MAPLE
isA122095 := proc(n) RETURN( isprime(n) and ( (2^n-1) mod (8*n+1)) = 0 ) ; end: n := 1 : for a from 2 to 500000 do if isA122095(a) then print(n, a) ; n := n+1 ; fi ; od ; # R. J. Mathar, Oct 20 2006
MATHEMATICA
Select[Prime[Range[1500]], Divisible[2^#-1, 8#+1]&] (* Harvey P. Dale, Dec 18 2012 *)
Select[Prime[Range[1500]], PowerMod[2, #, 8#+1]==1&] (* Harvey P. Dale, May 28 2015 *)
PROG
(PARI) forprime( p=1, 1e4, Mod(2, p*8+1)^p-1 || print1(p, ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
J. Lowell, Oct 17 2006
EXTENSIONS
More terms from R. J. Mathar, Oct 20 2006
STATUS
approved