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 A304939 Number of labeled nonempty hypertrees (connected antichains with no cycles) spanning some subset of {1,...,n} without singleton edges. 2
 1, 0, 1, 7, 51, 506, 6843, 118581, 2504855, 62370529, 1788082153, 57997339632, 2099638691439, 83922479506503, 3670657248913385, 174387350448735877, 8942472292255441103, 492294103555090048458, 28958704109012732921523 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Andrew Howroyd, Table of n, a(n) for n = 0..200 FORMULA a(n) = A305004(n) - 1 for n > 0. - Andrew Howroyd, Aug 27 2018 EXAMPLE The a(3) = 7 hypertrees are the following: {{1,2}} {{1,3}} {{2,3}} {{1,2,3}} {{1,2},{1,3}} {{1,2},{2,3}} {{1,3},{2,3}} PROG (PARI) \\ here b(n) is A030019 with b(1)=0. b(n)=if(n<2, n==0, sum(i=0, n, stirling(n-1, i, 2)*n^(i-1))); a(n)=if(n<1, n==0, sum(k=1, n, binomial(n, k)*b(k))); \\ Andrew Howroyd, Aug 27 2018 CROSSREFS Cf. A030019, A035053, A048143, A134954, A134955, A134956, A134957, A134959, A144959, A303838, A304867, A304911, A304912, A304918, A305004. Sequence in context: A219306 A246572 A230883 * A352358 A293073 A368286 Adjacent sequences: A304936 A304937 A304938 * A304940 A304941 A304942 KEYWORD nonn AUTHOR Gus Wiseman, May 21 2018 STATUS approved

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Last modified September 12 18:10 EDT 2024. Contains 375853 sequences. (Running on oeis4.)