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 A294381 Solution of the complementary equation a(n) = a(n-1)*b(n-2), where a(0) = 1, a(1) = 3, b(0) = 2, b(1) = 4. 7
 1, 3, 6, 24, 120, 840, 6720, 60480, 604800, 6652800, 79833600, 1037836800, 14529715200, 217945728000, 3487131648000, 59281238016000, 1067062284288000, 20274183401472000, 405483668029440000, 8515157028618240000, 187333454629601280000, 4308669456480829440000, 107716736412020736000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The complementary sequences a() and b() are uniquely determined by the titular equation and initial values. The initial values of each sequence in the following guide are a(0) = 1, a(2) = 3, b(0) = 2, b(1) = 4: A294381:  a(n) = a(n-1)*b(n-2) A294382:  a(n) = a(n-1)*b(n-2) - 1 A294383:  a(n) = a(n-1)*b(n-2) + 1 A294384:  a(n) = a(n-1)*b(n-2) - n A294385:  a(n) = a(n-1)*b(n-2) + n LINKS Jack W Grahl, Table of n, a(n) for n = 0..49 Clark Kimberling, Complementary equations, J. Int. Seq. 19 (2007), 1-13. EXAMPLE a(0) = 1, a(1) = 3, b(0) = 2, b(1) = 4, so that a(2) = a(1)*b(0) = 6. Complement: (b(n)) = (2, 4, 5, 7, 8, 9, 10, 12, 13, 14, 15, 16, ...). MATHEMATICA mex := First[Complement[Range[1, Max[#1] + 1], #1]] &; a = 1; a = 3; b = 2; b = 4; a[n_] := a[n] = a[n - 1]*b[n - 2]; b[n_] := b[n] = mex[Flatten[Table[Join[{a[n]}, {a[i], b[i]}], {i, 0, n - 1}]]]; Table[a[n], {n, 0, 40}]  (* A294381 *) Table[b[n], {n, 0, 10}] CROSSREFS Cf. A293076, A293765. Sequence in context: A295761 A262349 A109155 * A081072 A000717 A076020 Adjacent sequences:  A294378 A294379 A294380 * A294382 A294383 A294384 KEYWORD nonn,easy AUTHOR Clark Kimberling, Oct 29 2017 EXTENSIONS More terms from Jack W Grahl, Apr 26 2018 STATUS approved

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Last modified October 17 11:44 EDT 2019. Contains 328108 sequences. (Running on oeis4.)