A113534 Ascending descending base exponent transform of the flipped tribonacci substitution (A092782).

1, 3, 6, 7, 20, 10, 39, 12, 26, 19, 20, 43, 21, 78, 24, 53, 30, 57, 43, 88, 61, 59, 56, 43, 90, 42, 155, 46, 109, 53, 122, 75, 105, 114, 73, 122, 62, 197, 63, 172, 71, 136, 96, 183, 140, 122, 139, 86, 179, 81, 304, 83, 185, 98, 153, 162, 160, 261, 121, 192, 107, 236, 126

Offset: 1

Author

Jonathan Vos Post, Jan 13 2006

Keywords

• easy
• nonn

Comments

The flipped tribonacci substitution (A092782) b(n) is the fixed point of the morphism 1 -> 12, 2 -> 13, 3 -> 1, starting from b(1) = 1. The transformed sequence a(n) satisfies n <= a(n) <= 27 n but the bound can be determined to be much tighter.

Examples

			a(1) = A092782(1)^A092782(1) = 1^1 = 1.
a(2) = A092782(1)^A092782(2) + A092782(2)^A092782(1) = 1^2 + 2^1 = 3.
a(3) = 1^1 + 2^2 + 1^1 = 6.
a(4) = 1^3 + 2^1 + 1^2 + 3^1 = 7.
a(5) = 1^1 + 2^3 + 1^1 + 3^2 + 1^1 = 20.
a(6) = 1^2 + 2^1 + 1^3 + 3^1 + 1^2 + 2^1 = 10.
a(7) = 1^1 + 2^2 + 1^1 + 3^3 + 1^1 + 2^2 + 1^1 = 39.
a(8) = 1^1 + 2^1 + 1^2 + 3^1 + 1^3 + 2^1 + 1^2 + 1^1 = 12.
a(9) = 1^2 + 2^1 + 1^1 + 3^2 + 1^1 + 2^3 + 1^1 + 1^2 + 2^1 = 26.
a(10) = 1^1 + 2^2 + 1^1 + 3^1 + 1^2 + 2^1 + 1^3 + 1^1 + 2^2 + 1^1 = 19.
a(11) = 1^3 + 2^1 + 1^2 + 3^1 + 1^1 + 2^2 + 1^1 + 1^3 + 2^1 + 1^2 + 3^1 = 20.
a(12) = 1^1 + 2^3 + 1^1 + 3^2 + 1^1 + 2^1 + 1^2 + 1^1 + 2^3 + 1^1 + 3^2 + 1^1 = 43.
		

Links

• V. F. Sirvent, Semigroups and the self-similar structure of the flipped tribonacci substitution, Applied Math. Letters, 12 (1999), 25-29. [Contains many further references.]

Crossrefs

Cf. A005408, A087316, A092782, A113122, A113153, A113154, A113208, A113231, A113257, A113258, A113271, A113320, A113336, A113498.

Programs

Mathematica

A092782[n_] := Nest[Function[l, {Flatten[(l /. {1 -> {1, 2}, 2 -> {1, 3}, 3 -> {1}})]}], {1}, n][[1]]; Table[Sum[(A092782[k][[k]])^((A092782[n - k + 1][[n - k + 1]])), {k, 1, n}], {n, 1, 10}] (* G. C. Greubel, May 18 2017 *)

Formula

a(n) = Sum_{k=1..n} A092782(k)^(A092782(n-k+1)). - G. C. Greubel, May 17 2017

Extensions

a(3) corrected by Giovanni Resta, Jun 13 2016

a(13) onward from G. C. Greubel, May 18 2017