A274166 Number of real integers in n-th generation of tree T(i+1) defined in Comments.

1, 1, 1, 1, 1, 2, 3, 4, 8, 15, 24, 44, 84, 146, 254, 443, 761, 1317, 2262

Offset

0,6

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.

Links

Table of n, a(n) for n=0..18.

Example

If r = i+1, then g(3) = {3,2r,r+1, r^2}, in which the number of real integers is a(3) = 1.

Mathematica

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

Crossrefs

Cf. A274142.

Sequence in context: A161460 A097029 A122774 * A364595 A352817 A189740

Adjacent sequences: A274163 A274164 A274165 * A274167 A274168 A274169

Keyword

nonn,more

Author

Clark Kimberling, Jun 13 2016

Status

approved