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 A064670 Triangle T(n,k) (1 <= k <= n) where the first column (T(n,1)) is the sequence of secant numbers A000364. 0
 1, 1, 4, 5, 20, 36, 61, 244, 504, 576, 1385, 5540, 11916, 17280, 14400, 50521, 202084, 442224, 697536, 792000, 518400, 2702765, 10811060, 23870196, 39202560, 50198400, 47174400, 25401600, 199360981, 797443924, 1769923944 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Replacing m*m by m*(m+1) in the formula, the first column gives the tangent numbers A000182. LINKS FORMULA T(n+1, m) = m*m*Sum_{k = m-1, n} T(n, k) (T(n, 0) = 0). EXAMPLE T(4,3) = 9*(T(3,2) + (T(3,3)) = 9*(20+36) = 504. MATHEMATICA T[1, 1] = 1; T[n_, k_] /; 1 <= k <= n := T[n, k] = k^2*Sum[T[n-1, j], {j, k-1, n-1}]; T[_, _] = 0; Table[T[n, k], {n, 1, 8}, {k, 1, n}] // Flatten (* Jean-François Alcover, Oct 25 2016 *) CROSSREFS Cf. A064190, A000182, A000354. Sequence in context: A059182 A027958 A293942 * A119283 A151499 A057781 Adjacent sequences:  A064667 A064668 A064669 * A064671 A064672 A064673 KEYWORD easy,nice,nonn,tabl AUTHOR Jose L. Arregui (arregui(AT)posta.unizar.es), Oct 09 2001 EXTENSIONS More terms from Philippe Deléham, Sep 22 2005 STATUS approved

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Last modified February 23 05:58 EST 2019. Contains 320411 sequences. (Running on oeis4.)