A221578 A sum over partitions (q=6), see first comment.

1, 5, 35, 210, 1290, 7735, 46620, 279685, 1679370, 10076190, 60464670, 362787810, 2176773305, 13060638360, 78364108620, 470184650495, 2821109573550, 16926657432510, 101559954663930, 609359727929610, 3656158427989830, 21936950567886270, 131621703769781995

Offset

0,2

Comments

Set q=6 and f(m)=q^(m-1)*(q-1), then a(n) is the sum over all partitions P of n over all products Product_{k=1..L} f(m_k) where L is the number of different parts in the partition P = [p_1^m_1, p_2^m_2, ..., p_L^m_L].

Setting q to a prime power gives the sequence "Number of conjugacy classes in GL(n,q)":

q=3: A006952, q=4: A049314, q=5: A049315, q=7: A049316, q=8: A182603,

q=9: A182604, q=11: A182605, q=13: A182606, q=16: A182607, q=17: A182608,

q=19: A182609, q=23: A182610, q=25: A182611, q=27: A182612.

Sequences where q is not a prime power:

q=6: A221578, q=10: A221579, q=12: A221580,

q=14: A221581, q=15: A221582, q=18: A221583, q=20: A221584.

Links

Alois P. Heinz, Table of n, a(n) for n = 0..400

Maple

with(numtheory):
b:= proc(n) b(n):= add(phi(d)*6^(n/d), d=divisors(n))/n-1 end:
a:= proc(n) a(n):= `if`(n=0, 1,
       add(add(d*b(d), d=divisors(j)) *a(n-j), j=1..n)/n)
    end:
seq(a(n), n=0..30);  # Alois P. Heinz, Jan 24 2013

Mathematica

b[n_] := Sum[EulerPhi[d]*6^(n/d), {d, Divisors[n]}]/n-1; a[n_] := a[n] = If[n == 0, 1, Sum[Sum[d*b[d], {d, Divisors[j]}]*a[n-j], {j, 1, n}]/n]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Feb 17 2014, after Alois P. Heinz *)

Prog

(PARI)
N=66; x='x+O('x^N);
gf=prod(n=1, N, (1-x^n)/(1-6*x^n)  );
v=Vec(gf)

Crossrefs

Sequence in context: A038143 A352404 A356391 * A320071 A024062 A180250

Adjacent sequences: A221575 A221576 A221577 * A221579 A221580 A221581

Keyword

nonn

Author

Joerg Arndt, Jan 20 2013

Status

approved