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A120331 Number of polynomials in two noncommuting variables over the field F_2 having complexity or rank n. 1
1, 1, 6, 72, 1776, 89280, 9065472, 1850148864, 757046525952, 620298979246080, 1017126921430892544, 3336658943759213395968, 21894988380633154342354944, 287369531352172835754234347520, 7543680108676972971562235527692288 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

R. Bacher, Table of n, a(n) for n = 0..24

R. Bacher, The special subgroup of invertible non-commutative rational power series as a metric group, arXiv:0804.1092

FORMULA

The reference contains a somewhat complicated formula.

EXAMPLE

The six polynomials corresponding to a(2) are: X, Y, X+Y, 1+X, 1+Y, 1+X+Y.

CROSSREFS

Cf. A137342.

Sequence in context: A012242 A138446 A099029 * A009523 A009793 A259212

Adjacent sequences:  A120328 A120329 A120330 * A120332 A120333 A120334

KEYWORD

nonn

AUTHOR

Roland Bacher, Apr 29 2008

STATUS

approved

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Last modified July 17 14:44 EDT 2019. Contains 325106 sequences. (Running on oeis4.)