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A349488
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Number of unlabeled disconnected P-series with n elements.
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6
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0, 1, 2, 6, 16, 45, 115, 296, 733, 1801, 4338, 10380, 24531, 57622, 134317, 311465, 718297, 1649579, 3772448, 8597284, 19527774, 44225665, 99885035, 225032910, 505797776, 1134419571, 2539173978, 5672736196, 12650878942, 28165845957, 62609097765, 138963709623
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OFFSET
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1,3
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LINKS
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FORMULA
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MAPLE
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b:= proc(n) option remember; `if`(n=0, 1, add(b(n-j)*add(d*
max(1, 2^(d-1)-1), d=numtheory[divisors](j)), j=1..n)/n)
end:
a:= n-> b(n)-max(1, 2^(n-1)-1):
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MATHEMATICA
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b[n_] := b[n] = If[n == 0, 1, Sum[b[n - j]*Sum[d*
Max[1, 2^(d-1) - 1], {d, Divisors[j]}], {j, 1, n}]/n];
a[n_] := b[n] - Max[1, 2^(n-1)-1];
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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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