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 A009692 Number of partitions of {1, 2, ..., 2n} into pairs whose differences are primes. 4
 1, 0, 1, 3, 10, 40, 153, 921, 5144, 30717, 230748, 1766056, 14052445, 116580521, 897876519, 7657321097, 75743979608, 788733735080, 7569825650083, 75242386295617, 831978453306391, 9444103049405370, 120064355466770831, 1579842230380587833 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Table of n, a(n) for n=0..23. EXAMPLE a(3) = 3: {{1,6}, {2,4}, {3,5}}, {{1,4}, {2,5}, {3,6}}, {{1,3}, {2,5}, {4,6}}. - Alois P. Heinz, Nov 15 2016 MAPLE b:= proc(s) option remember; `if`(s={}, 1, (j-> add(`if`(i b({\$1..2*n}): seq(a(n), n=0..12); # Alois P. Heinz, Nov 15 2016 MATHEMATICA b[s_] := b[s] = If[s == {}, 1, Function[j, Sum[If[i < j && PrimeQ[j - i], b[s ~Complement~ {i, j}], 0], {i, s}]][Max[s]]]; a[n_] := b[Range[2n]]; Table[Print[n, " ", a[n]]; a[n], {n, 0, 18}] (* Jean-François Alcover, Mar 01 2021, after Alois P. Heinz *) CROSSREFS Cf. A000341. Sequence in context: A099763 A318118 A149052 * A149053 A149054 A149055 Adjacent sequences: A009689 A009690 A009691 * A009693 A009694 A009695 KEYWORD nonn,hard AUTHOR David W. Wilson EXTENSIONS a(0), a(14)-a(18) from Alois P. Heinz, Nov 15 2016 a(19)-a(23) from Bert Dobbelaere, Feb 20 2020 STATUS approved

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Last modified November 30 23:40 EST 2023. Contains 367464 sequences. (Running on oeis4.)