A096142 Let p(0) = 1, p(k) = k-th prime for k >= 1; write 2n = p(i) + p(j) with i <= j and i minimal; sequence gives i.

0, 0, 0, 0, 2, 0, 0, 2, 0, 0, 2, 0, 2, 3, 0, 0, 2, 3, 0, 2, 0, 0, 2, 0, 2, 3, 0, 2, 3, 0, 0, 2, 3, 0, 2, 0, 0, 2, 3, 0, 2, 0, 2, 3, 0, 2, 3, 4, 0, 2, 0, 0, 2, 0, 0, 2, 0, 2, 3, 4, 6, 5, 6, 0, 2, 0, 2, 3, 0, 0, 2, 3, 4, 5, 0, 0, 2, 3, 0, 2, 3, 0, 2, 0, 2, 3, 0, 2, 3, 0, 0, 2, 3, 4, 5, 0, 0, 2, 0

Offset: 1

Author

David Stroup, Jul 23 2004

Keywords

• easy
• nonn

Examples

			a(14)=3, because 28=5+23 (3rd and 9th prime) and 28-1, 28-2, 28-3 are not primes.
		

Programs

PARI

a(n) = {tn = 2 * n; ideb = 0; ok = 0; while (! ok, if (ideb == 0, pj = tn -1, pj = tn - prime(ideb)); if (isprime(pj) || (pj == 1), ok = 1, ideb++);); return (ideb);} \\ Michel Marcus, Aug 29 2013

Extensions

Terms corrected by Michel Marcus, Aug 29 2013