OFFSET
1,1
COMMENTS
It is conjectured that a(n) = 3 for infinitely many n.
EXAMPLE
n=1: 2 // 3 // 3 = 233, which is prime, so a(1) = 3.
n=2: 3 // 5 // 2 = 352, which is not prime, but 3 // 5 // 3 = 353 is, so a(2) = 3.
PROG
(Sage)
concat = lambda xx: Integer(''.join(map(str, xx)))
A174034 = lambda x: next((p for p in Primes() if is_prime(concat([nth_prime(x), nth_prime(x+1), p])))) # D. S. McNeil, Dec 02 2010
(PARI) A174034(n)={ n=eval(Str(prime(n), prime(n+1))); for( d=1, 99, n*=10; forprime( p=10^(d-1), 10^d, isprime(n+p) & return(p)))} \\ M. F. Hasler, Dec 01 2010
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Mar 06 2010
EXTENSIONS
Edited and terms checked by D. S. McNeil, Dec 01 2010
STATUS
approved