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A335045
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Minimal common prime of two Goldbach partitions of 2n and 2(n+1) or zero if no common prime exists.
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1
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0, 3, 3, 5, 7, 3, 5, 7, 3, 5, 7, 23, 11, 13, 3, 5, 7, 0, 11, 13, 3, 5, 7, 47, 11, 13, 53, 17, 19, 3, 5, 7, 0, 11, 13, 3, 5, 7, 0, 11, 13, 83, 17, 19, 89, 23, 37, 0, 29, 31, 3, 5, 7, 3, 5, 7, 113, 11, 13, 0, 17, 19, 0, 23, 31, 131, 29, 31, 3, 5, 7, 0, 11, 13, 3, 5, 7, 0, 11, 13, 0, 17, 19, 167, 23, 37, 173
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OFFSET
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2,2
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COMMENTS
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a(n) is the least prime p such that 2n-p is in A001359, or 0 if no such p exists. - Robert Israel, May 21 2020
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LINKS
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EXAMPLE
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4 = 2+2 and 6 = 3+3. Since those are the only available Goldbach partitions and they have no common prime, a(4/2) = a(2) = 0.
14 = 3+11 and 16 = 3+13, so a(14/2) = a(7) = 3.
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MAPLE
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N:= 100:
P:= select(isprime, {seq(i, i=3..2*N-1, 2)}):
T:= P intersect map(`-`, P, 2):
f:= n -> subs(infinity=0, min(P intersect map(t -> 2*n-t, T))):
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MATHEMATICA
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d[n_]:=Flatten[Cases[FrobeniusSolve[{1, 1}, 2*n], {__?PrimeQ}]]
e[n_]:=Intersection[d[n], d[n+1]]; f[n_]:=If[e[n]=={}, 0, Min[e[n]]]; f/@Range[2, 100]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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