A091238 Number of nodes in rooted tree with GF2X-Matula number n.

1, 2, 3, 3, 5, 4, 4, 4, 6, 6, 4, 5, 6, 5, 7, 5, 9, 7, 5, 7, 7, 5, 8, 6, 5, 7, 8, 6, 6, 8, 5, 6, 7, 10, 9, 8, 7, 6, 8, 8, 7, 8, 7, 6, 10, 9, 5, 7, 7, 6, 11, 8, 7, 9, 6, 7, 10, 7, 7, 9, 6, 6, 9, 7, 11, 8, 8, 11, 7, 10, 8, 9, 6, 8, 12, 7, 9, 9, 8, 9, 11, 8, 9, 9, 13, 8, 10, 7, 8, 11, 8, 10, 8, 6, 9, 8

Offset

1,2

Comments

Each n occurs A000081(n) times.

Links

Table of n, a(n) for n=1..96.

A. Karttunen, Scheme-program for computing this sequence.

Index entries for sequences operating on GF(2)[X]-polynomials

Example

GF2X-Matula numbers for unoriented rooted trees are constructed otherwise just like the standard Matula-Goebel numbers (cf. A061773), but instead of normal factorization in N, one factorizes in polynomial ring GF(2)[X] as follows. Here IR(n) is the n-th irreducible polynomial (A014580(n)) and X stands for GF(2)[X]-multiplication (A048720):
................................................o...................o
................................................|...................|
............o...............o...o........o......o...............o...o
............|...............|...|........|......|...............|...|
...o........o......o...o....o...o....o...o......o......o.o.o....o...o
...|........|.......\./......\./......\./.......|.......\|/......\./.
x..x........x........x........x........x........x........x........x..
1..2 = IR(1)..3 = IR(2)..4 = 2 X 2....5 = 3 X 3....6 = 2 X 3....7 = IR(3)..8 = 2 X 2 X 2..9 = 3 X 7
Counting the vertices (marked with x's and o's) of each tree above, we get the eight initial terms of this sequence: 1,2,3,3,5,4,4,4,6.

Crossrefs

a(n) = A061775(A091205(n)). a(A091230(n)) = n+1. Cf. A091239-A091241.

Sequence in context: A330834 A056149 A167494 * A178047 A122954 A268087

Adjacent sequences: A091235 A091236 A091237 * A091239 A091240 A091241

Keyword

nonn

Author

Antti Karttunen, Jan 03 2004

Status

approved