OFFSET
1,1
COMMENTS
Primes prime(k) such that prime(k) == 1 (mod A001223(k)).
Problem: are there infinitely many such primes?
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
N:= 1000: # to get all terms <= N
P:= select(isprime, [2, seq(i, i=3..nextprime(N), 2)]):
P[select(i -> (P[i] - 1) mod (P[i+1]-P[i]) = 0, [$1..nops(P)-1])];
MATHEMATICA
Select[Partition[Prime[Range[100]], 2, 1], GCD[#[[1]]-1, #[[2]]-1] == #[[2]]- #[[1]]&][[All, 1]] (* Harvey P. Dale, Apr 18 2018 *)
PROG
(PARI) is(n) = ispseudoprime(n) && gcd(n-1, nextprime(n+1)-1)==nextprime(n+1)-n \\ Felix Fröhlich, Aug 06 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Thomas Ordowski and Robert Israel, Aug 05 2016
STATUS
approved