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A326996
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Main diagonal of A260876.
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3
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1, 1, 4, 365, 3086331, 5612271711927, 3829797188212731601783, 1478967550753025951356611840021161, 452501475882033837823819972299248189399008553836, 146630849220097180917463638217405949960396188742877031073909770851
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refs;
listen;
history;
text;
internal format)
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = (n^2)! * [x^(n^2)] exp(Sum_{k>=1} x^(n*k) / (n*k)!). - Ilya Gutkovskiy, Feb 09 2020
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MAPLE
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b:= proc(n, k) option remember; `if`(n=0, 1, add(
binomial(k*n-1, k*j-1)*b(n-j, k), j=1..n))
end:
a:= n-> b(n$2):
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MATHEMATICA
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b[n_, k_] := b[n, k] = If[n == 0, 1, Sum[Binomial[k n - 1, k j - 1] b[n - j, k], {j, 1, n}]];
a[n_] := b[n, n];
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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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