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 A263985 Triangle of signed Eulerian numbers on involutions, read by rows. 0
 1, -1, 1, -1, -2, 1, 1, -2, -2, 1, 1, 6, 0, -2, 1, -1, 3, 14, 2, -3, 1, -1, -12, -15, 12, -1, -4, 1, 1, -4, -51, -76, 4, -3, -4, 1, 1, 20, 67, -10, -80, 30, 3, -4, 1, -1, 5, 137, 517, 414, 66, 75, 7, -5, 1, -1, -30, -192, -140, 721, 588, -49, 44, 0, -6, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 LINKS M. Barnabei, F. Bonetti, M. Silimbani, The signed Eulerian numbers on involutions, PU. M. A. Vol. 19 (2008) pp. 117-126. M. Barnabei, F. Bonetti, M. Silimbani, The signed Eulerian numbers on involutions, arXiv:0803.2126 [math.CO], 2008. J. Desarmenien and D. Foata, The signed Eulerian numbers, Discrete Math. 99 (1992), no. 1-3, 49-58. FORMULA T(n, k) = Sum_{m=0..k+1} (-1)^(k-m+1)*C(n+1,k-m+1)*Sum_{j=0..floor(n/2)} (-1)^j*C(C(m+1,2)+j-1,j)*C(m,n-2*j); EXAMPLE Triangle begins: 1; -1, 1; -1, -2, 1; 1, -2, -2, 1; 1, 6, 0, -2, 1; -1, 3, 14, 2, -3, 1; -1, -12, -15, 12, -1, -4, 1; ... MATHEMATICA T[n_, k_] := Sum[(-1)^(k-m+1) Binomial[n+1, k-m+1] Sum[(-1)^j Binomial[ Binomial[m+1, 2]+j-1, j] Binomial[m, n-2j], {j, 0, n/2}], {m, 0, k+1}]; Table[T[n, k], {n, 1, 11}, {k, 0, n-1}] // Flatten (* Jean-François Alcover, Sep 26 2018 *) PROG (PARI) T(n, k) = sum(m=0, k+1, (-1)^(k-m+1)*binomial(n+1, k-m+1)*sum(j=0, n\2, (-1)^j*binomial(binomial(m+1, 2)+j-1, j)*binomial(m, n-2*j))); CROSSREFS Cf. A049061. Sequence in context: A051287 A278218 A216031 * A176261 A264837 A264714 Adjacent sequences:  A263982 A263983 A263984 * A263986 A263987 A263988 KEYWORD sign,tabl AUTHOR Michel Marcus, Oct 31 2015 STATUS approved

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Last modified December 5 03:59 EST 2021. Contains 349530 sequences. (Running on oeis4.)