A296843 Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n+1), where a(0) = 1, a(1) = 2, b(0) = 3, b(1) = 4, b(2) = 5, b(3) = 6, and (a(n)) and (b(n)) are increasing complementary sequences.

1, 2, 9, 18, 35, 63, 109, 184, 306, 504, 825, 1345, 2187, 3551, 5758, 9330, 15110, 24463, 39597, 64085, 103708, 167820, 271556, 439405, 710991, 1150427, 1861450, 3011910, 4873394, 7885340, 12758771, 20644149, 33402959, 54047148, 87450148, 141497338

Offset

0,2

Comments

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.

Links

Clark Kimberling, Table of n, a(n) for n = 0..1000

Clark Kimberling, Complementary equations, J. Int. Seq. 19 (2007), 1-13.

Example

a(0) = 1, a(1) = 2, b(0) = 3, b(1) = 4, b(2) = 5, b(3) = 6
a(2) = a(0) + a(1) + b(3) = 9
Complement: (b(n)) = (3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 19, 20, ...)

Mathematica

a[0] = 1; a[1] = 2; b[0] = 3; b[1] = 4; b[2] = 5; b[3] = 6;
a[n_] := a[n] = a[n - 1] + a[n - 2] + b[n + 1];
j = 1; While[j < 16, 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}];  (* A296843 *)
Table[b[n], {n, 0, 20}] (* complement *)

Crossrefs

Cf. A001622, A296245, A296844, A296845.

Sequence in context: A294535 A294543 A295956 * A200085 A083708 A280588

Adjacent sequences: A296840 A296841 A296842 * A296844 A296845 A296846

Keyword

nonn,easy

Author

Clark Kimberling, Jan 12 2018

Status

approved