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 A086764 Triangle T(n, k), read by row, related to Euler's difference table A068106 (divide k-th diagonal of A068106 by k!). 20
 1, 0, 1, 1, 1, 1, 2, 3, 2, 1, 9, 11, 7, 3, 1, 44, 53, 32, 13, 4, 1, 265, 309, 181, 71, 21, 5, 1, 1854, 2119, 1214, 465, 134, 31, 6, 1, 14833, 16687, 9403, 3539, 1001, 227, 43, 7, 1, 133496, 148329, 82508, 30637, 8544, 1909, 356, 57, 8, 1, 1334961, 1468457, 808393 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,7 COMMENTS The k-th column sequence, k >= 0, without leading zeros, enumerates the ways to distribute n beads, n >= 1, labeled differently from 1 to n, over a set of (unordered) necklaces, excluding necklaces with exactly one bead, and k+1 indistinguishable, ordered, fixed cords, each allowed to have any number of beads. Beadless necklaces as well as beadless cords each contribute a factor 1, hence for n=0 one has 1. See A000255 for the description of a fixed cord with beads. This comment derives from a family of recurrences found by Malin Sjodahl for a combinatorial problem for certain quark and gluon diagrams (Feb 27 2010). - Wolfdieter Lang, Jun 02 2010 LINKS Indranil Ghosh, Rows 0..50, flattened W. Y. C. Chen et al., Higher-order log-concavity in Euler's difference table, Discrete Math., 311 (2011), 2128-2134. (These are the numbers d^k_n.) Fanja Rakotondrajao, k-Fixed-Points-Permutations, Integers: Electronic journal of combinatorial number theory 7 (2007) A36. FORMULA T(n, n) = 1; T(n+1, n) = n; T(n+2, n) = A002061(n+1) = n^2 + n + 1; T(n+3, n) = n^3 + 3*n^2 + 5*n + 2. T(n, k) = (k + 1)*T(n, k + 1)-T(n-1, k); T(n, n) = 1; T(n, k) = 0, if k > n. T(n, k) = (n-1)*T(n-1, k) + (n-k-1)*T(n-2, k). k!*T(n, k) = A068106(n+1, k+1). Sum_{k>=0} T(n, k) = A003470(n+1). T(n, k) = (1/k!) * Sum_{j>=0} (-1)^j*binomial(n-k, j)*(n-j)!. - Philippe Deléham, Jun 13 2005 From Peter Bala, Aug 14 2008: (Start) The following remarks all relate to the array read as a square array: e.g.f for column k: exp(-y)/(1-y)^(k+1); e.g.f. for array: exp(-y)/(1-x-y) = (1 + x + x^2 + x^3 + ...) + (x + 2*x^2 + 3*x^3 + 4*x^4 + ...)*y + (1 + 3*x + 7*x^2 + 13*x^3 + ...)*y^2/2! + ... . This table is closely connected to the constant e. The row, column and diagonal entries of this table occur in series formulas for e. Row n for n >= 2: e = n!*(1/T(n,0) + (-1)^n*[1/(1!*T(n,0)*T(n,1)) + 1/(2!*T(n,1)*T(n,2)) + 1/(3!*T(n,2)*T(n,3)) + ...]). For example, row 3 gives e = 6*(1/2 - 1/(1!*2*11) - 1/(2!*11*32) - 1/(3!*32*71) - ...). See A095000. Column 0: e = 2 + Sum_{n>=2} (-1)^n*n!/(T(n,0)*T(n+1,0)) = 2 + 2!/(1*2) - 3 !/(2*9) + 4!/(9*44) - ... . Column k, k >= 1: e = (1 + 1/1! + 1/2! + ... + 1/k!) + 1/k!*Sum_{n >= 0} (-1)^n*n!/(T(n,k)*T(n+1,k)). For example, column 3 gives e = 8/3 + 1/6*(1/(1*3) - 1/(3*13) + 2/(13*71) - 6/(71*465) + ...). Main diagonal: e = 1 + 2*(1/(1*1) - 1/(1*7) + 1/(7*71) - 1/(71*1001) + ...). First subdiagonal: e = 8/3 + 5/(3*32) - 7/(32*465) + 9/(465*8544) - ... . Second subdiagonal: e = 2*(1 + 2^2/(1*11) - 3^2/(11*181) + 4^2/(181*3539) - ...). See A143413. Third subdiagonal: e = 3 - (2*3*5)/(2*53) + (3*4*7)/(53*1214) - (4*5*9)/(1214*30637) + ... . For the corresponding results for the constants 1/e, sqrt(e) and 1/sqrt(e) see A143409, A143410 and A143411 respectively. For other arrays similarly related to constants see A008288 (for log(2)), A108625 (for zeta(2)) and A143007 (for zeta(3)). (End) G.f. for column k is hypergeom([1,k+1],[],x/(x+1))/(x+1). - Mark van Hoeij, Nov 07 2011 T(n, k) = (n!/k!)*hypergeom([k-n], [-n], -1). - Peter Luschny, Oct 05 2017 EXAMPLE 1; 0, 1; 1, 1, 1; 2, 3, 2, 1; 9, 11, 7, 3, 1; 44, 53, 32, 13, 4, 1; ... Formatted as a square array:       1      3     7    13   21   31  43 57 which equals A002061       2     11    32    71  134  227 356 which equals A094792       9     53   181   465 1001 1909 which equals A094793      44    309  1214  3539 8544 which equals A094794     265   2119  9403 30637 which equals A023043    1854  16687 82508 which equals A023044   14833 148329 which equals A023045 Formatted as a triangular array (mirror of A076731):        1        0      1        1      1     1        2      3     2     1        9     11     7     3    1       44     53    32    13    4    1      265    309   181    71   21    5   1     1854   2119  1214   465  134   31   6  1    14833  16687  9403  3539 1001  227  43  7 1   133496 148329 82508 30637 8544 1909 356 57 8 1 MATHEMATICA T[n_, k_]:=(1/k!)*Sum[(-1)^j*Binomial[n-k, j]*(n-j)!, {j, 0, n}]; Flatten[Table[T[n, k], {n, 0, 11}, {k, 0, n}]] (* Indranil Ghosh, Feb 20 2017 *) T[n_, k_] := (n!/k!) HypergeometricPFQ[{k-n}, {-n}, -1]; Table[T[n, k], {n, 0, 9}, {k, 0, n}] // Flatten (* Peter Luschny, Oct 05 2017 *) CROSSREFS Columns: A000166, A000155, A000153, A000261, A001909, A001910, A176732 - A176736. Cf. A068106, A003470, A002061. Mirror image of A076731. Cf. A143409, A143410, A143411, A143413. Sequence in context: A291087 A020858 A090664 * A255010 A292371 A216683 Adjacent sequences:  A086761 A086762 A086763 * A086765 A086766 A086767 KEYWORD easy,nonn,tabl AUTHOR Philippe Deléham, Aug 02 2003 EXTENSIONS More terms from David Wasserman, Mar 28 2005 Additional comments from Zerinvary Lajos, Mar 30 2006 Edited by N. J. A. Sloane, Sep 24 2011 STATUS approved

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Last modified October 22 22:34 EDT 2019. Contains 328335 sequences. (Running on oeis4.)