A001172 Smallest even number that is an unordered sum of two odd primes in exactly n ways.

0, 6, 10, 22, 34, 48, 60, 78, 84, 90, 114, 144, 120, 168, 180, 234, 246, 288, 240, 210, 324, 300, 360, 474, 330, 528, 576, 390, 462, 480, 420, 570, 510, 672, 792, 756, 876, 714, 798, 690, 1038, 630, 1008, 930, 780, 960, 870, 924, 900, 1134, 1434, 840, 990, 1302

Offset: 0

Author

N. J. A. Sloane, Eric Wolman, Dec 17 1969

Keywords

• nonn
• nice
• look
• easy

Comments

a(n) = A023036(n) for all n > 1.

References

• N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• T. D. Noe, Table of n, a(n) for n = 0..10000
• Eric Wolman, Letter to N. J. A. Sloane, 1970.
• Index entries for sequences related to Goldbach conjecture

Crossrefs

Cf. A000954, A000974, A002375, A005843, A023036.

Divided by 2: A258713.

Programs

Mathematica

nn = 55; a = Table[0, {nn}]; n = 6; While[Times @@ a == 0, c = 0; k = 3; While[k <= n/2, If[PrimeQ[k] && PrimeQ[n - k], c++]; k++]; If[c <= nn && a[[c]] == 0, a[[c]] = n]; n = n + 2]; Prepend[a, 0]

Extensions

a(0) corrected by Zak Seidov, Sep 30 2011