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A296264
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Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-2)*b(n-1), where a(0) = 2, a(1) = 4, b(0) = 1, b(1) = 3, and (a(n)) and (b(n)) are increasing complementary sequences.
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2
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2, 4, 9, 28, 67, 137, 260, 477, 847, 1456, 2459, 4097, 6766, 11103, 18141, 29550, 48033, 77963, 126416, 204841, 331763, 537156, 869519, 1407325, 2277546, 3685654, 5964070, 9650654, 15615716, 25267426, 40884264, 66152880, 107038404, 173192616, 280232426
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OFFSET
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0,1
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COMMENTS
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The increasing complementary sequences a() and b() are uniquely determined by the titular equation and initial values. a(n)/a(n-1) -> (1 + sqrt(5))/2 = golden ratio (A001622). See A296245 for a guide to related sequences.
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LINKS
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EXAMPLE
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a(0) = 2, a(1) = 4, b(0) = 2, b(1) = 1, b(2) = 3;
a(2) = a(0) + a(1) + b(0)*b(1) = 9;
Complement: (b(n)) = (1, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, ...)
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MATHEMATICA
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a[0] = 2; a[1] = 4; b[0] = 1; b[1] = 3;
a[n_] := a[n] = a[n - 1] + a[n - 2] + b[n - 1] b[n - 2];
j = 1; While[j < 10, k = a[j] - j - 1;
While[k < a[j + 1] - j + 1, b[k] = j + k + 2; k++]; j++];
u = Table[a[n], {n, 0, k}]; (* A296264 *)
Table[b[n], {n, 0, 20}] (* complement *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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