A024684 Number of ways prime(n) is a sum of three distinct primes.

0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 6, 9, 11, 13, 13, 15, 18, 17, 19, 25, 26, 28, 32, 31, 37, 32, 39, 44, 51, 54, 48, 60, 55, 62, 64, 73, 80, 79, 74, 89, 84, 92, 86, 92, 107, 119, 105, 118, 122, 117, 135, 143, 146, 147, 141, 149, 159, 157, 176, 175, 190, 180

Offset

1,9

Links

Zak Seidov and T. D. Noe, Table of n, a(n) for n = 1..10000 (first 2000 terms from Zak Seidov)

Wikipedia, Goldbach's weak conjecture

Formula

a(n) = A125688(prime(n)). - R. J. Mathar, Jun 09 2014

Example

a(9) = 2 because prime(9) = 23 and 23 = 3 + 7 + 13 = 5 + 7 + 11.

Mathematica

last = 313; pp = PrimePi[last]; t = Select[Sort[Tally[Select[Total /@ Subsets[Prime[Range[2, pp]], {3}], PrimeQ]]], #[[1]] <= last &]; Join[{0, 0, 0, 0, 0, 0, 0}, Transpose[t][[2]]] (* T. D. Noe, Apr 15 2013 *)

Crossrefs

Cf. A002372, A002375, A224534.

Sequence in context: A122168 A017856 A087412 * A265538 A037850 A037886

Adjacent sequences: A024681 A024682 A024683 * A024685 A024686 A024687

Keyword

nonn

Author

Clark Kimberling

Status

approved