A154804 Number of ways to represent 2*n as the sum of two distinct primes (counting 1 as a prime).

0, 1, 1, 2, 1, 2, 2, 2, 3, 3, 2, 4, 2, 2, 4, 3, 3, 4, 2, 3, 5, 4, 3, 6, 4, 3, 6, 3, 3, 7, 3, 5, 6, 3, 5, 7, 5, 5, 7, 5, 4, 9, 4, 4, 10, 4, 4, 7, 4, 6, 9, 6, 5, 9, 7, 7, 11, 6, 5, 12, 3, 5, 10, 4, 7, 10, 5, 5, 9, 8, 7, 11, 5, 5, 13, 5, 8, 11, 5, 8, 10, 6, 5, 14, 9, 6, 12, 7, 6, 15, 7, 8, 13, 5, 8, 12, 7, 9

Offset: 1

Author

Omar E. Pol, Jan 16 2009

Keywords

• nonn

Comments

Number of ways to represent 2*n as the sum of two distinct noncomposite numbers. - Omar E. Pol, Dec 11 2024

Crossrefs

Cf. A008578, A154720, A154721, A154722, A154723.

Formula

a(n) = A101264(n-1) + A061357(n). [From R. J. Mathar, Jan 21 2009]

a(n) = A001031(n) - A080339(n).

Extensions

More terms from R. J. Mathar, Jan 21 2009

Edited by Franklin T. Adams-Watters, Jan 31 2009