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A319226
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Irregular triangle where T(n,k) is the number of acyclic spanning subgraphs of a cycle graph, where the sizes of the connected components are given by the integer partition with Heinz number A215366(n,k).
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14
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1, 2, 1, 3, 3, 1, 4, 2, 4, 4, 1, 5, 5, 5, 5, 5, 5, 1, 6, 6, 6, 3, 2, 6, 12, 9, 6, 6, 1, 7, 7, 7, 7, 14, 7, 7, 7, 7, 7, 21, 14, 7, 7, 1, 8, 8, 8, 4, 8, 8, 8, 16, 16, 8, 2, 24, 8, 24, 12, 16, 8, 32, 20, 8, 8, 1, 9, 9, 9, 9, 9, 9, 18, 9, 9, 9, 18, 18, 3, 27, 27
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OFFSET
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1,2
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COMMENTS
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A refinement of A135278, up the sign these are the coefficients appearing in the expansion of power-sum symmetric functions in terms of elementary or homogeneous symmetric functions.
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LINKS
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EXAMPLE
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Triangle begins:
1
2 1
3 3 1
4 2 4 4 1
5 5 5 5 5 5 1
6 6 6 3 2 6 12 9 6 6 1
The fourth row corresponds to the symmetric function identities:
p(4) = -4 e(4) + 2 e(22) + 4 e(31) - 4 e(211) + e(1111)
p(4) = 4 h(4) - 2 h(22) - 4 h(31) + 4 h(211) - h(1111).
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MATHEMATICA
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primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
csm[s_]:=With[{c=Select[Tuples[Range[Length[s]], 2], And[OrderedQ[#], UnsameQ@@#, Length[Intersection@@s[[#]]]>0]&]}, If[c=={}, s, csm[Union[Append[Delete[s, List/@c[[1]]], Union@@s[[c[[1]]]]]]]]];
Table[Length[Select[Subsets[Partition[Range[n], 2, 1, 1], {n-PrimeOmega[m]}], Sort[Length/@csm[Union[#, List/@Range[n]]]]==primeMS[m]&]], {n, 6}, {m, Sort[Times@@Prime/@#&/@IntegerPartitions[n]]}]
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CROSSREFS
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Cf. A005651, A008480, A048994, A056239, A124794, A124795, A135278, A215366, A318762, A319191, A319193, A319225.
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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