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A022901 Number of solutions to c(1)*prime(3)+...+c(n)*prime(n+2) = 1, where c(i) = +-1 for i>1, c(1) = 1. 1
0, 0, 1, 0, 0, 0, 3, 0, 3, 0, 6, 0, 35, 0, 88, 0, 351, 0, 1144, 0, 3570, 0, 13281, 0, 45712, 0, 161985, 0, 574357, 0, 1993704, 0, 7191396, 0, 26481567, 0, 95441234, 0, 352520549, 0, 1296413520, 0, 4775354550, 0, 17754091585, 0, 65964401274, 0, 245645895029, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..500

EXAMPLE

a(7) counts these 3 solutions: {5, -7, 11, 13, -17, 19, -23}, {5, 7, -11, -13, 17, 19, -23}, {5, 7, -11, 13, -17, -19, 23}.

MATHEMATICA

{f, s} = {3, 1}; Table[t = Map[Prime[# + f - 1] &, Range[2, z]]; Count[Map[Apply[Plus, #] &, Map[t # &, Tuples[{-1, 1}, Length[t]]]], s - Prime[f]], {z, 22}]

(* A022901, a(n) = number of solutions of "sum = s" using Prime(f) to Prime(f+n-1) *)

n = 7; t = Map[Prime[# + f - 1] &, Range[n]]; Map[#[[2]] &, Select[Map[{Apply[Plus, #], #} &, Map[t # &, Map[Prepend[#, 1] &, Tuples[{-1, 1}, Length[t] - 1]]]], #[[1]] == s &]]  (* the 3 solutions of using n=7 primes; Peter J. C. Moses, Oct 01 2013 *)

CROSSREFS

Sequence in context: A100258 A045763 A132748 * A055945 A138123 A328382

Adjacent sequences:  A022898 A022899 A022900 * A022902 A022903 A022904

KEYWORD

nonn

AUTHOR

Clark Kimberling

EXTENSIONS

Corrected and extended by Clark Kimberling, Oct 01 2013

a(23)-a(50) from Alois P. Heinz, Aug 06 2015

STATUS

approved

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Last modified January 24 10:24 EST 2020. Contains 331193 sequences. (Running on oeis4.)