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A242587 The number of conjugacy classes of n X n matrices over F_3. 13
1, 3, 12, 39, 129, 399, 1245, 3783, 11514, 34734, 104754, 314922, 946623, 2842077, 8532147, 25603788, 76830033, 230513439, 691598901, 2074870002, 6224790639, 18674600664, 56024355396, 168073769199, 504222998115, 1512671142432, 4538018555652, 13614062210490 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Apparently the Euler transform of A001867.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..1000

K. E. Morrison, Integer sequences and matrices over finite fields, J. Int. Seq. 9 (2006) # 06.2.1, Section 1.16.

FORMULA

G.f.: 1/Product_{r>=1} (1-3*x^r).

a(n) = S(n,1), where S(n,m) = sum(k=m..n/2, 3*S(n-k,k))+3, S(n,n)=3, S(0,m)=1, S(n,m)=0 for n<m. - Vladimir Kruchinin, Sep 07 2014

a(n) ~ c * 3^n, where c = Product_{k>=1} 1/(1-1/3^k) = 1.7853123419985341903674... . - Vaclav Kotesovec, Mar 19 2015

G.f.: Sum_{i>=0} 3^i*x^i/Product_{j=1..i} (1 - x^j). - Ilya Gutkovskiy, Apr 12 2018

MAPLE

A242587 := proc(n)

local r, x ;

if n = 0 then

1;

else

1/mul(1-3*x^r, r=1..n) ;

convert(%, parfrac, x) ;

coeftayl(%, x=0, n) ;

end if;

end proc:

# second Maple program:

b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,

b(n, i-1) +`if`(i>n, 0, 3*b(n-i, i))))

end:

a:= n-> b(n$2):

seq(a(n), n=0..50); # Alois P. Heinz, Sep 07 2014

MATHEMATICA

b[n_, i_] := b[n, i] = If[n==0, 1, If[i<1, 0, b[n, i-1] + If[i>n, 0, 3*b[n-i, i]]]] ; a[n_] := b[n, n]; Table[a[n], {n, 0, 50}] (* Jean-François Alcover, Apr 03 2015, after Alois P. Heinz *)

(O[x]^20 - 2/QPochhammer[3, x])[[3]] (* Vladimir Reshetnikov, Nov 20 2015 *)

PROG

(Maxima)

S(n, m):=if n=0 then 1 else if n<m then 0 else if n=m then 3 else sum(3*S(n-k, k), k, m, n/2)+3;

makelist(S(n, 1), n, 0, 17); /* Vladimir Kruchinin, Sep 07 2014 */

CROSSREFS

Cf. A070933 (over F_2).

Column k=3 of A246935.

Sequence in context: A029858 A123109 A240806 * A330169 A290906 A110153

Adjacent sequences: A242584 A242585 A242586 * A242588 A242589 A242590

KEYWORD

nonn

AUTHOR

R. J. Mathar, May 18 2014

STATUS

approved

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Last modified December 1 06:17 EST 2022. Contains 358454 sequences. (Running on oeis4.)