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A327382
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Number of colored integer partitions of n such that four colors are used and parts differ by size or by color.
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6
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1, 4, 14, 36, 85, 180, 360, 680, 1234, 2160, 3674, 6092, 9882, 15724, 24594, 37884, 57553, 86344, 128060, 187948, 273178, 393516, 562158, 796860, 1121375, 1567336, 2176664, 3004692, 4124130, 5630160, 7646916, 10335696, 13905376, 18625564, 24843142, 33003072
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OFFSET
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4,2
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COMMENTS
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LINKS
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FORMULA
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a(n) ~ exp(2*Pi*sqrt(n/3)) / (8 * 3^(1/4) * n^(3/4)). - Vaclav Kotesovec, Sep 14 2019
G.f.: (-1 + Product_{m >= 1} (1 + x^m))^4. - George Beck, Jan 29 2021
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MAPLE
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b:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0, add((t->
b(t, min(t, i-1), k)*binomial(k, j))(n-i*j), j=0..min(k, n/i))))
end:
a:= n-> (k-> add(b(n$2, k-i)*(-1)^i*binomial(k, i), i=0..k))(4):
seq(a(n), n=4..45);
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MATHEMATICA
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b[n_, i_, k_] := b[n, i, k] = If[n == 0, 1, If[i < 1, 0, Sum[With[{t = n - i j}, b[t, Min[t, i - 1], k] Binomial[k, j]], {j, 0, Min[k, n/i]}]]];
a[n_] := With[{k = 4}, Sum[b[n, n, k-i] (-1)^i Binomial[k, i], {i, 0, k}]];
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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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