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A221583
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A sum over partitions (q=18), see first comment.
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9
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1, 17, 323, 5814, 104958, 1889227, 34011900, 612213877, 11019954438, 198359179578, 3570467115834, 64268408079198, 1156831379431973, 20822964829665048, 374813367546080412, 6746640615829343087, 121439531095946141922, 2185911559727028566514
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OFFSET
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0,2
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COMMENTS
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Set q=18 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)":
Sequences where q is not a prime power:
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LINKS
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MAPLE
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with(numtheory):
b:= proc(n) b(n):= add(phi(d)*18^(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:
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MATHEMATICA
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b[n_] := Sum[EulerPhi[d]*18^(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 *)
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PROG
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(PARI)
N=66; x='x+O('x^N);
gf=prod(n=1, N, (1-x^n)/(1-18*x^n) );
v=Vec(gf)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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