A046921 Number of ways to express 2n+1 as p+2a^2; p = 1 or prime, a >= 0.

1, 2, 2, 2, 2, 2, 3, 2, 1, 4, 3, 2, 3, 1, 2, 4, 2, 2, 4, 3, 2, 3, 3, 2, 4, 3, 2, 5, 1, 2, 6, 3, 1, 3, 4, 2, 5, 4, 2, 6, 3, 2, 4, 2, 3, 6, 2, 1, 4, 3, 4, 6, 4, 2, 6, 5, 2, 6, 3, 2, 5, 1, 2, 3, 5, 4, 5, 4, 1, 8, 4, 1, 6, 3, 2, 6, 2, 2, 6, 6, 1, 4, 5, 3, 7, 4, 3, 6, 2, 3, 10, 2, 3, 4, 4, 3, 3, 4, 2

Offset: 0

Author

David W. Wilson

Keywords

• nonn

Comments

Goldbach conjectured this sequence is never zero.

The only zero terms appear to be for the odd numbers 5777 and 5993. - T. D. Noe, Aug 23 2008

Links

• T. D. Noe, Table of n, a(n) for n = 0..10000
• L. Hodges, A lesser-known Goldbach conjecture, Math. Mag., 66 (1993), 45-47.
• Index entries for sequences related to Goldbach conjecture

Crossrefs

Cf. A042978, A046920, A046922, A046923, A060003, A143539.

Cf. A007697.

Programs

Haskell

a046921 = a046920 . a005408  -- Reinhard Zumkeller, Apr 03 2013

Formula

a(n) = A046920(A005408(n)). - Reinhard Zumkeller, Apr 03 2013