A274149 Number of integers in n-th generation of tree T(-1/4) defined in Comments.

1, 1, 1, 1, 1, 2, 2, 3, 4, 6, 7, 9, 12, 17, 22, 29, 38, 51, 68, 90, 119, 158, 209, 277, 368, 489, 648, 858, 1137, 1509, 2002, 2655, 3520, 4667, 6189, 8208, 10885, 14436, 19141, 25382, 33659, 44638, 59195, 78497, 104092, 138036, 183050, 242745, 321904, 426875

Offset: 0

Author

Clark Kimberling, Jun 11 2016

Keywords

• nonn
• easy

Comments

Let T* be the infinite tree with root 0 generated by these rules: if p is in T*, then p+1 is in T* and x*p is in T*. Let g(n) be the set of nodes in the n-th generation, so that g(0) = {0}, g(1) = {1}, g(2) = {2,x}, g(3) = {3,2x,x+1,x^2}, etc. Let T(r) be the tree obtained by substituting r for x.

See A274142 for a guide to related sequences.

Examples

			For r = -1/4, we have g(3) = {3,2r,r+1, r^2}, in which the number of integers is a(3) = 1.
		

Links

• Kenny Lau, Table of n, a(n) for n = 0..8153

Crossrefs

Cf. A274142.

Programs

Mathematica

z = 18; t = Join[{{0}}, Expand[NestList[DeleteDuplicates[Flatten[Map[{# + 1, x*#} &, #], 1]] &, {1}, z]]];
u = Table[t[[k]] /. x -> -1/4, {k, 1, z}];
Table[Count[Map[IntegerQ, u[[k]]], True], {k, 1, z}]

Formula

a(n-1) = length of row n of the array in A274185.

Extensions

More terms from Kenny Lau, Jul 01 2016