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A223894
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Triangular array read by rows: T(n,k) is the number of connected components with size k summed over all simple labeled graphs on n nodes; n>=1, 1<=k<=n.
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4
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1, 2, 1, 6, 3, 4, 32, 12, 16, 38, 320, 80, 80, 190, 728, 6144, 960, 640, 1140, 4368, 26704, 229376, 21504, 8960, 10640, 30576, 186928, 1866256, 16777216, 917504, 229376, 170240, 326144, 1495424, 14930048, 251548592, 2415919104, 75497472, 11010048, 4902912, 5870592, 17945088, 134370432, 2263937328, 66296291072
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OFFSET
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1,2
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LINKS
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FORMULA
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E.g.f. for column k: A001187(n)*x^n/n!*A(x) where A(x) is the e.g.f. for A006125.
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EXAMPLE
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Triangle T(n,k) begins:
1;
2, 1;
6, 3, 4;
32, 12, 16, 38;
320, 80, 80, 190, 728;
6144, 960, 640, 1140, 4368, 26704;
229376, 21504, 8960, 10640, 30576, 186928, 1866256;
...
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MAPLE
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b:= proc(n) option remember; `if`(n=0, 1, 2^(n*(n-1)/2)-
add(k*binomial(n, k)* 2^((n-k)*(n-k-1)/2)*b(k), k=1..n-1)/n)
end:
T:= (n, k)-> binomial(n, k)*b(k)*2^((n-k)*(n-k-1)/2):
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MATHEMATICA
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nn = 9; f[list_] := Select[list, # > 0 &]; g = Sum[2^Binomial[n, 2] x^n/n!, {n, 0, nn}]; a = Drop[Range[0, nn]! CoefficientList[Series[Log[g] + 1, {x, 0, nn}], x], 1]; Map[f, Drop[Transpose[Table[Range[0, nn]! CoefficientList[Series[a[[n]] x^n/n! g, {x, 0, nn}], x], {n, 1, nn}]], 1]] // Grid
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PROG
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(Magma)
if n eq 0 then return 1;
else return 2^Binomial(n, 2) - (&+[Binomial(n-1, j-1)*2^Binomial(n-j, 2)*b(j): j in [0..n-1]]);
end if; return b;
end function;
A223894:= func< n, k | Binomial(n, k)*2^Binomial(n-k, 2)*b(k) >;
(SageMath)
@CachedFunction
if (n==0): return 1
else: return 2^binomial(n, 2) - sum(binomial(n-1, j-1)*2^binomial(n-j, 2)*b(j) for j in range(n))
def A223894(n, k): return binomial(n, k)*2^binomial(n-k, 2)*b(k)
flatten([[A223894(n, k) for k in range(1, n+1)] for n in range(1, 13)]) # G. C. Greubel, Oct 03 2022
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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