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 A220860 Triangle read by rows related to enumeration of permutations avoiding certain patterns. 0
 1, 1, 1, 1, 4, 1, 1, 10, 9, 1, 20, 41, 6, 1, 35, 133, 61, 2, 1, 56, 350, 336, 49, 1, 84, 798, 1336, 465, 20, 1, 120, 1638, 4300, 2789, 380, 4, 1, 165, 3102, 11902, 12577, 3581, 192, 1, 220, 5511, 29392, 46487, 22924, 3025, 56 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS See Barnabei et al. (2012) for precise definition. LINKS Table of n, a(n) for n=1..51. M. Barnabei, F. Bonetti and M. Silimbani, Two permutation classes related to the Bubble Sort operator, Electronic Journal of Combinatorics 19(3) (2012), #P25. See Theorem 6. EXAMPLE Triangle begins: 1 1 1 1 4 1 1 10 9 1 20 41 6 1 35 133 61 2 1 56 350 336 49 1 84 798 1336 465 20 1 120 1638 4300 2789 380 4 ... PROG (PARI) rows(nn) = {my(pol = Pol((1 - 3*x + 3*x^2 - 3*x^2*y - x^3 + 2*x^3*y - x^3*y^2)/(1 - 4*x + 6*x^2 - 4*x^2*y - 4*x^3 + 6*x^3*y - 2*x^3*y^2 + x^4 - 2*x^4*y + x^4*y^2) + O(x^nn))); for (i=1, poldegree(pol, x), ypol = polcoeff(pol, i, x); for (j=0, poldegree(ypol, y), print1(polcoeff(ypol, j, y), ", "); ); print(); ); } \\ Michel Marcus, Jul 23 2014 CROSSREFS Cf. A000292 (second column). Sequence in context: A361731 A109955 A214398 * A174043 A319029 A175124 Adjacent sequences: A220857 A220858 A220859 * A220861 A220862 A220863 KEYWORD nonn,tabf AUTHOR N. J. A. Sloane, Dec 25 2012 EXTENSIONS More terms from Michel Marcus, Jul 23 2014 Keyword set to tabf by Michel Marcus, Jul 23 2014 STATUS approved

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Last modified September 13 22:05 EDT 2024. Contains 375910 sequences. (Running on oeis4.)