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A059419 Triangle T(n,k) (1 <= k <= n) of tangent numbers, read by rows: T(n,k) = coefficient of x^n/n! in expansion of (tan x)^k/k!. 16

%I

%S 1,0,1,2,0,1,0,8,0,1,16,0,20,0,1,0,136,0,40,0,1,272,0,616,0,70,0,1,0,

%T 3968,0,2016,0,112,0,1,7936,0,28160,0,5376,0,168,0,1,0,176896,0,

%U 135680,0,12432,0,240,0,1,353792,0,1805056,0,508640,0,25872,0,330,0,1,0

%N Triangle T(n,k) (1 <= k <= n) of tangent numbers, read by rows: T(n,k) = coefficient of x^n/n! in expansion of (tan x)^k/k!.

%C (tan(x))^k = sum{n>0, If n+k is odd, T(n,k) = 0 = n!/k!*(-1)^((n+k)/2)*sum{j=k..n} (j!/n!) * Stirling2(n,j) * 2^(n-j) * (-1)^(n+j-k) * binomial(j-1,k-1)*x^n}. - _Vladimir Kruchinin_, Aug 13 2012

%C Also the Bell transform of A009006(n+1). For the definition of the Bell transform see A264428. - _Peter Luschny_, Jan 26 2016

%D L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 259.

%H Peter Bala, <a href="/A112007/a112007.txt">Diagonals of triangles with generating function exp(t*F(x)).</a>

%H Vladimir Kruchinin, <a href="https://arxiv.org/abs/1009.2565">Composition of ordinary generating functions</a>, arXiv:1009.2565 [math.CO], 2010.

%H Toufik Mansour, Mark Shattuck, <a href="https://doi.org/10.22108/toc.2017.102359.1483">Combinatorial parameters on bargraphs of permutations</a>, Transactions on Combinatorics, Article 1, Vol. 7, Issue 2, June 2018, Page 1-16.

%F T(n+1, k) = T(n, k-1) + k*(k+1)*T(n, k+1), T(n, n) = 1.

%F If n+k is odd, T(n,k) = 0 = 1/k!*(-1)^((n+k)/2)*Sum_{j=k..n} j!* Stirling2(n,j)*2^(n-j)*(-1)^(n+j-k)*binomial(j-1,k-1). - _Vladimir Kruchinin_, Feb 10 2011

%F E.g.f.: exp(t*tan(x))-1 = t*x + t^2*x^2/2! + (2*t + t^3)*x^3/3! + ....

%F The row polynomials are given by D^n(exp(x*t)) evaluated at x = 0, where D is the operator (1+x^2)*d/dx. - _Peter Bala_, Nov 25 2011

%F The o.g.f.s of the diagonals of this triangle are rational functions obtained from the series reversion (x-t*tan(x))^(-1) = x/(1-t) + 2*t/(1-t)^4*x^3/3! + 8*t*(2+3*t)/(1-t)^7*x^5/5! + 16*t*(17+78*t+45*t^2)/(1-t)^10*x^7/7! + .... For example, the fourth subdiagonal has o.g.f. 8*t*(2+3*t)/(1-t)^7 = 16*t + 136*t^2 + 616*t^3 + .... - _Peter Bala_, Apr 23 2012

%F With offset 0 and initial column of zeros, except for T(0,0) = 1, e.g.f.(t,x) = e^(x*tan(t)) = e^(P(.,x)t) ; the lowering operator, L = atan(d/dx) ; and the raising operator, R = x [1 +(d/dx)^2], where L P(n,x) = n P(n-1,x) and R P(n,x) = P(n+1,x). The sequence is a binomial Sheffer sequence. - _Tom Copeland_, Oct 01 2015

%e 1;

%e 0, 1;

%e 2, 0, 1;

%e 0, 8, 0, 1;

%e 16, 0, 20, 0, 1;

%e 0, 136, 0, 40, 0, 1;

%e 272, 0, 616, 0, 70, 0, 1;

%e 0, 3968, 0, 2016, 0, 112, 0, 1;

%e 7936, 0, 28160, 0, 5376, 0, 168, 0, 1;

%p A059419 := proc(n,k) option remember; if n = k then 1; elif k <0 or k > n then 0; else procname(n-1,k-1)+k*(k+1)*procname(n-1,k+1) ; end if; end proc: # _R. J. Mathar_, Feb 11 2011

%p # The function BellMatrix is defined in A264428.

%p # Adds (1, 0, 0, 0, ..) as column 0.

%p BellMatrix(n -> 2^(n+1)*abs(euler(n+1, 1)), 10); # _Peter Luschny_, Jan 26 2016

%t d[f_ ] := (1+x^2)*D[f, x]; d[ f_, n_] := Nest[d, f, n]; row[n_] := Rest[ CoefficientList[ d[Exp[x*t], n] /. x -> 0, t]]; Flatten[ Table[ row[n], {n, 1, 12}]] (* _Jean-Fran├žois Alcover_, Dec 21 2011, after _Peter Bala_ *)

%t rows = 12;

%t t = Table[2^(n+1)*Abs[EulerE[n+1, 1]], {n, 0, rows}];

%t T[n_, k_] := BellY[n, k, t];

%t Table[T[n, k], {n, 1, rows}, {k, 1, n}] // Flatten (* _Jean-Fran├žois Alcover_, Jun 22 2018, after _Peter Luschny_ *)

%o (PARI) T(n,k)=if(k<1 || k>n,0,n!*polcoeff(tan(x+x*O(x^n))^k/k!,n))

%o (Sage)

%o def A059419_triangle(dim):

%o M = matrix(SR,dim,dim)

%o for n in (0..dim-1): M[n,n] = 1

%o for n in (1..dim-1):

%o for k in (0..n-1):

%o M[n,k] = M[n-1,k-1]+(k+1)*(k+2)*M[n-1,k+1]

%o return M

%o A059419_triangle(9) # _Peter Luschny_, Sep 19 2012

%Y Diagonals give A000182, A024283, A059420 (interspersed with 0's), also A007290, A059421. Row sums give A006229. Essentially the same triangle as A008308.

%Y A111593 (signed triangle with extra column k=0 and row n=0).

%K nonn,easy,nice,tabl

%O 1,4

%A _N. J. A. Sloane_, Jan 30 2001

%E More terms from Larry Reeves (larryr(AT)acm.org), Feb 01 2001

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Last modified August 21 22:52 EDT 2018. Contains 313958 sequences. (Running on oeis4.)