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A292698
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Number of solutions to 3 +- 7 +- 13 +- 19 +- ... +- prime(4*n) = 0.
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3
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0, 0, 0, 1, 2, 8, 27, 83, 292, 944, 3279, 11291, 38992, 138066, 490248, 1757360, 6347321, 22998089, 83780199, 306819363, 1128999790, 4174251748, 15507225620, 57767819903, 215327188611, 803901214851, 3013081897103, 11331883386143, 42737620941612
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OFFSET
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1,5
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LINKS
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FORMULA
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Constant term in the expansion of 1/2 * Product_{k=1..2*n} (x^prime(2*k) + 1/x^prime(2*k)).
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EXAMPLE
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For n = 4 the solution is 3 - 7 - 13 + 19 - 29 + 37 + 43 - 53 = 0.
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MAPLE
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s:= proc(n) s(n):= `if`(n=0, 0, ithprime(2*n)+s(n-1)) end:
b:= proc(n, i) option remember; `if`(n>s(i), 0, `if`(i=0, 1,
(p-> b(n+p, i-1)+b(abs(n-p), i-1))(ithprime(2*i))))
end:
a:= n-> b(0, 2*n)/2:
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MATHEMATICA
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s[n_] := s[n] = If[n == 0, 0, Prime[2n] + s[n-1]];
b[n_, i_] := b[n, i] = If[n > s[i], 0, If[i == 0, 1,
With[{p = Prime[2i]}, b[n+p, i-1] + b[Abs[n-p], i-1]]]];
a[n_] := b[0, 2n]/2;
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PROG
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(PARI) {a(n) = 1/2*polcoeff(prod(k=1, 2*n, x^prime(2*k)+1/x^prime(2*k)), 0)}
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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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