%I #9 Feb 22 2018 22:40:53

%S 2,4,12,23,43,75,128,214,354,582,951,1549,2517,4084,6620,10724,17365,

%T 28111,45499,73635,119160,192822,312010,504861,816901,1321793,2138726,

%U 3460552,5599312,9059899,14659247,23719183,38378468,62097690,100476198,162573929

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

%C 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).

%C See A295862 for a guide to related sequences.

%H Clark Kimberling, <a href="/A295954/b295954.txt">Table of n, a(n) for n = 0..2000</a>

%H Clark Kimberling, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL10/Kimberling/kimberling26.html">Complementary equations</a>, J. Int. Seq. 19 (2007), 1-13.

%e a(0) = 2, a(1) = 4, b(0) = 1, b(1) = 3, b(2) = 5

%e b(3) = 6 (least "new number")

%e a(2) = a(1) + a(0) + b(2) + 1 = 12

%e Complement: (b(n)) = (1, 3, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, ...)

%t a[0] = 2; a[1] = 4; b[0] = 1; b[1] = 3; b[2] = 5;

%t a[n_] := a[n] = a[n - 1] + a[n - 2] + b[n] + 1;

%t j = 1; While[j < 6, k = a[j] - j - 1;

%t While[k < a[j + 1] - j + 1, b[k] = j + k + 2; k++]; j++];

%t Table[a[n], {n, 0, k}]; (* A295954 *)

%Y Cf. A001622, A000045, A295862.

%K nonn,easy

%O 0,1

%A _Clark Kimberling_, Dec 08 2017