OFFSET
1,2
COMMENTS
Numbers k such that (6k)^2 + 1 is prime and p = 6k-1 and q = 6k+1 are twin primes.
Numbers k such that p*q + 2 is prime, where p = 6k-1 and q = 6k+1 are twin primes.
LINKS
Robert G. Wilson v, Table of n, a(n) for n = 1..1000
FORMULA
a(n) == 0 (mod 5) for n > 1.
a(n+1) = 5 * A125251(n).
MATHEMATICA
fQ[n_] := AllTrue[{30n -1, 30n +1, 900n^2 +1}, PrimeQ]; Join[{1}, 5*Select[ Range@1200, fQ]] (* Robert G. Wilson v, Mar 19 2017 *)
PROG
(PARI) print1(1, ", "); for(n=1, 15000, if(isprime(30*n-1)&& isprime(30*n+1)&& isprime(900*n^2+1), print1(5*n, ", ")));
CROSSREFS
KEYWORD
nonn
AUTHOR
Thomas Ordowski and Altug Alkan, Mar 19 2017
STATUS
approved