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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,14

COMMENTS

This is related to the conjecture given in A223174 and A223175.

For n > 8, a(12) = a(24) = 0 because A223174(12)= A223174(24)= 0.

LINKS

Michel Lagneau, Table of n, a(n) for n = 0..10000

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

CROSSREFS

Cf. A219254, A223174, A223175.

Sequence in context: A330348 A117229 A264119 * A269972 A202205 A336123

Adjacent sequences:  A225515 A225516 A225517 * A225519 A225520 A225521

KEYWORD

nonn

AUTHOR

Michel Lagneau, May 09 2013

STATUS

approved

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Last modified July 24 23:25 EDT 2021. Contains 346273 sequences. (Running on oeis4.)