

A294564


Solution of the complementary equation a(n) = a(n1) + a(n2) + 2*b(n1)  b(n2)  1, where a(0) = 1, a(1) = 2, b(0) = 3, and (a(n)) and (b(n)) are increasing complementary sequences.


2



1, 2, 7, 14, 27, 50, 86, 146, 243, 401, 657, 1074, 1747, 2838, 4603, 7460, 12083, 19564, 31669, 51256, 82949, 134230, 217205, 351464, 568698, 920192, 1488921, 2409145, 3898099, 6307278, 10205412, 16512726, 26718175, 43230939, 69949153, 113180132, 183129326
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OFFSET

0,2


COMMENTS

The increasing complementary sequences a() and b() are uniquely determined by the titular equation and initial values. See A294532 for a guide to related sequences. Conjecture: a(n)/a(n1) > (1 + sqrt(5))/2 = golden ratio (A001622).


LINKS

Table of n, a(n) for n=0..36.
Clark Kimberling, Complementary equations, J. Int. Seq. 19 (2007), 113.


EXAMPLE

a(0) = 1, a(1) = 2, b(0) = 3, so that
b(1) = 4 (least "new number")
a(2) = a(1) + a(0) + 2*b(1)  b(0)  1 = 7
Complement: (b(n)) = (3, 4, 5, 6, 8, 10, 11, 12, 13, 15, 16, ...)


MATHEMATICA

mex := First[Complement[Range[1, Max[#1] + 1], #1]] &;
a[0] = 1; a[1] = 3; b[0] = 2;
a[n_] := a[n] = a[n  1] + a[n  2] + 2 b[n  1]  b[n  2]  1;
b[n_] := b[n] = mex[Flatten[Table[Join[{a[n]}, {a[i], b[i]}], {i, 0, n  1}]]];
Table[a[n], {n, 0, 40}] (* A294564 *)
Table[b[n], {n, 0, 10}]


CROSSREFS

Cf. A001622, A294532.
Sequence in context: A210728 A294533 A294541 * A068040 A200084 A184704
Adjacent sequences: A294561 A294562 A294563 * A294565 A294566 A294567


KEYWORD

nonn,easy


AUTHOR

Clark Kimberling, Nov 15 2017


STATUS

approved



