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 A164652 Triangle read by rows: Hultman numbers: a(n,k) is the number of permutations of n elements whose cycle graph (as defined by Bafna and Pevzner) contains k cycles for n >= 0 and 1 <= k <= n+1. 8
 1, 0, 1, 1, 0, 1, 0, 5, 0, 1, 8, 0, 15, 0, 1, 0, 84, 0, 35, 0, 1, 180, 0, 469, 0, 70, 0, 1, 0, 3044, 0, 1869, 0, 126, 0, 1, 8064, 0, 26060, 0, 5985, 0, 210, 0, 1, 0, 193248, 0, 152900, 0, 16401, 0, 330, 0, 1, 604800, 0, 2286636, 0, 696905, 0, 39963, 0, 495, 0, 1, 0, 19056960, 0, 18128396, 0, 2641925, 0, 88803, 0, 715, 0, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,8 COMMENTS a(n,k) is also the number of ways to express a given (n+1)-cycle as the product of an (n+1)-cycle and a permutation with k cycles (see Doignon and Labarre). a(n,n+1-2k) is the number of permutations of n elements whose block-interchange distance is k (see Christie, Doignon and Labarre). LINKS Reinhard Zumkeller, Rows n = 0..125 of triangle, flattened N. Alexeev, A. Pologova, M. A. Alekseyev, Generalized Hultman Numbers and Cycle Structures of Breakpoint Graphs, Journal of Computational Biology 24:2 (2017), 93-105; arXiv, arXiv:1503.05285 [q-bio.GN], 2015-2017. N. Alexeev, P. Zograf, Hultman numbers, polygon gluings and matrix integrals, arXiv preprint arXiv:1111.3061 [math.PR], 2011. N. Alexeev, P. Zograf, Random matrix approach to the distribution of genomic distance, Journal of Computational Biology 21:8 (2014), 622-631. M. Bona and R. Flynn, The Average Number of Block Interchanges Needed to Sort A Permutation and a recent result of Stanley, arXiv:0811.0740 [math.CO], 2008. M. Bona and R. Flynn, The Average Number of Block Interchanges Needed to Sort A Permutation and a recent result of Stanley, Inf. Process. Lett., 109 (2009), 927-931 D. A. Christie, Sorting Permutations by Block-Interchanges, Inf. Process. Lett. 60 (1996), 165-169 J.-P. Doignon and A. Labarre, On Hultman Numbers, J. Integer Seq., 10 (2007), 13 pages. Simona Grusea and Anthony Labarre, The distribution of cycles in breakpoint graphs of signed permutations, arXiv:1104.3353 [cs.DM], 2011-2012. FORMULA T(n,k) = S1(n+2,k)/C(n+2,2) if n-k is odd, and 0 otherwise. Here S1(n,k) are the unsigned Stirling numbers of the first kind A132393 and C(n,k) is the binomial coefficient (see Bona and Flynn). For n > 0: T(n,k) = A128174(n+1,k) * A130534(n+1,k-1) / A000217(n+1). - Reinhard Zumkeller, Aug 01 2014 EXAMPLE Triangle begins: n=0:  1; n=1:  0, 1; n=2:  1, 0, 1; n=3:  0, 5, 0, 1; n=4:  8, 0, 15, 0, 1; n=5:  0, 84, 0, 35, 0, 1; n=6:  180, 0, 469, 0, 70, 0, 1; n=7:  0, 3044, 0, 1869, 0, 126, 0, 1; n=8:  8064, 0, 26060, 0, 5985, 0, 210, 0, 1; n=9:  0, 193248, 0, 152900, 0, 16401, 0, 330, 0, 1; n=10: 604800, 0, 2286636, 0, 696905, 0, 39963, 0, 495, 0, 1;   ... MAPLE A164652:= (n, k)-> `if`(n-k mod 2 = 1, -Stirling1(n+2, k)/binomial(n+2, 2), 0): for n from 0 to 7 do seq(A164652(n, k), k=1..n+1) od; # Peter Luschny, Mar 22 2015 MATHEMATICA T[n_, k_] := If[OddQ[n-k], Abs[StirlingS1[n+2, k]]/Binomial[n+2, 2], 0]; Table[T[n, k], {n, 0, 11}, {k, 1, n+1}] // Flatten (* Jean-François Alcover, Aug 10 2018 *) PROG (Haskell) a164652 n k = a164652_tabl !! n !! k a164652_row n = a164652_tabl !! n a164652_tabl = [0] : tail (zipWith (zipWith (*)) a128174_tabl \$    zipWith (map . flip div) (tail a000217_list) (map init \$ tail a130534_tabl)) -- Reinhard Zumkeller, Aug 01 2014 (Sage) def A164652(n, k):     return stirling_number1(n+2, k)/binomial(n+2, 2) if is_odd(n-k) else 0 for n in (0..7): print([A164652(n, k) for k in (1..n+1)]) # Peter Luschny, Mar 22 2015 (PARI) T(n, k)= my(s=(n-k)%2); (-1)^s*s*stirling(n+2, k, 1)/binomial(n+2, 2); concat(vector(12, n, vector(n, k, T(n-1, k)))) \\ Gheorghe Coserea, Jan 23 2018 CROSSREFS Cf. A000142 (row sums), A000217, A060593, A128174, A130534, A185259, A189507, A260695. Sequence in context: A083861 A097591 A318299 * A127557 A060524 A133843 Adjacent sequences:  A164649 A164650 A164651 * A164653 A164654 A164655 KEYWORD nonn,tabl,changed AUTHOR Anthony Labarre, Aug 19 2009 EXTENSIONS T(0,1) set to 1 by Peter Luschny, Mar 24 2015 Edited to match values of k to the range 1 to n+1. - Max Alekseyev, Nov 20 2020 STATUS approved

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Last modified November 29 19:26 EST 2020. Contains 338769 sequences. (Running on oeis4.)