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A295145 Solution of the complementary equation a(n) = a(n-1) + 2*a(n-2) + b(n-2), where a(0) = 1, a(1) = 2, b(0) = 3, b(1) = 4, and (a(n)) and (b(n)) are increasing complementary sequences. 5
1, 2, 7, 15, 34, 70, 146, 295, 597, 1198, 2404, 4813, 9635, 19277, 38564, 77136, 154283, 308575, 617162, 1234334, 2468681, 4937373, 9874760, 19749532, 39499079, 78998171, 157996358 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
The increasing complementary sequences a() and b() are uniquely determined by the titular equation and initial values. See A295053 for a guide to related sequences.
LINKS
Clark Kimberling, Complementary equations, J. Int. Seq. 19 (2007), 1-13.
FORMULA
a(n+1)/a(n) -> 2.
EXAMPLE
a(0) = 1, a(1) = 2, b(0) = 3, b(1) = 4
a(2) = a(1) + 2*a(0) + b(0) = 7
Complement: (b(n)) = (3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, ...)
MATHEMATICA
mex := First[Complement[Range[1, Max[#1] + 1], #1]] &;
a[0] = 1; a[1] = 2; b[0] = 3; b[1] = 4;
a[n_] := a[n] = a[ n - 1] + 2 a[n - 2] + 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, 18}] (* A295145 *)
Table[b[n], {n, 0, 10}]
CROSSREFS
Sequence in context: A345448 A209633 A216633 * A151998 A308631 A052130
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Nov 19 2017
STATUS
approved

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Last modified April 18 08:27 EDT 2024. Contains 371769 sequences. (Running on oeis4.)