

A225518


Number of ways to express 2n+1 as p + 8*q, with p and q primes.


1



0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 2, 2, 1, 1, 2, 1, 1, 1, 2, 2, 3, 0, 1, 3, 1, 2, 3, 2, 3, 1, 2, 3, 2, 1, 2, 3, 1, 1, 3, 2, 3, 1, 2, 3, 3, 2, 4, 2, 2, 2, 4, 2, 3, 3, 2, 4, 3, 2, 4, 3, 3, 4, 2, 2, 3, 2, 2, 4, 3, 2, 5, 3, 2, 4, 5, 3, 4, 2, 4, 5, 4, 2, 4, 3
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OFFSET

0,14


COMMENTS



LINKS



EXAMPLE

a(14) = 2 because 29 = 5+8*3 = 13+8*2 with 2 decompositions.
a(23) = 3 because 47 = 7+8*5 = 23+8*3 = 31+8*2 with 3 decompositions.


MATHEMATICA

a[n_] := (ways = 0; Do[p = 2k + 1; q = (nk)/4; If[PrimeQ[p] && PrimeQ[q], ways++], {k, 1, n}]; ways); Table[a[n], {n, 0, 90}]


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



