OFFSET
1,2
EXAMPLE
1 is a term because 2*prime(1) - 1 = 3 (prime) and 2*prime(1) + 1 = 5 (prime);
2 is a term because 2*prime(2) - 1 = 5 (prime) and 2*prime(2) + 1 = 7 (prime),
7 is a term because 2*prime(7) - 1 = 33 (composite) and 2*prime(7) + 1 = 35 (composite).
MAPLE
for n from 1 to 200 do p := ithprime(n) ; if isprime(2*p-1) = isprime(2*p+1) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Apr 20 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Apr 14 2010
EXTENSIONS
Corrected (6 inserted, 74 inserted) by R. J. Mathar, Apr 20 2010
STATUS
approved