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A295147 Solution of the complementary equation a(n) = a(n-1) + 2*a(n-2) + b(n-1), 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, 8, 17, 39, 80, 167, 337, 682, 1368, 2745, 5495, 11000, 22006, 44024, 88055, 176123, 352254, 704522, 1409053, 2818121, 5636252, 11272520, 22545051, 45090119, 90180250, 180360518 (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(1) = 8
Complement: (b(n)) = (3, 4, 5, 6, 7, 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 - 1];
b[n_] := b[n] = mex[Flatten[Table[Join[{a[n]}, {a[i], b[i]}], {i, 0, n - 1}]]];
Table[a[n], {n, 0, 18}] (* A295147 *)
Table[b[n], {n, 0, 10}]
CROSSREFS
Sequence in context: A061150 A160189 A281470 * A215933 A328742 A341506
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Nov 19 2017
STATUS
approved

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Last modified May 27 02:41 EDT 2024. Contains 372847 sequences. (Running on oeis4.)