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 A000506 One half of the number of permutations of [n] such that the differences have 5 runs with the same signs. (Formerly M5322 N2313) 3
 61, 841, 7311, 51663, 325446, 1910706, 10715506, 58258210, 309958755, 1623847695, 8412276585, 43220104041, 220683627988, 1121561317408, 5679711010548, 28683869195556, 144552802373145, 727271783033445 (list; graph; refs; listen; history; text; internal format)
 OFFSET 6,1 REFERENCES L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 260, #13 F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied Tables, Cambridge, 1966, p. 260. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS FORMULA Lim_{n->infinity} 16*a(n)/5^n = 1. - Philippe Deléham, Feb 22 2004 MATHEMATICA p[n_ /; n >= 2, 1] = 2; p[n_ /; n >= 2, k_] /; 1 <= k <= n := p[n, k] = k*p[n-1, k] + 2*p[n-1, k-1] + (n-k)*p[n-1, k-2]; p[n_, k_] = 0; t[n_, k_] := p[n, k]/2; a[n_] := t[n, 5]; Table[a[n], {n, 6, 23}] (* Jean-François Alcover, Feb 09 2016 *) CROSSREFS A diagonal of A008970. Sequence in context: A251426 A232858 A093473 * A008358 A317283 A264306 Adjacent sequences:  A000503 A000504 A000505 * A000507 A000508 A000509 KEYWORD nonn,easy AUTHOR EXTENSIONS More terms from Emeric Deutsch, Feb 21 2004 STATUS approved

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Last modified January 18 07:18 EST 2019. Contains 319269 sequences. (Running on oeis4.)