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A082137
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Square array of transforms of binomial coefficients, read by antidiagonals.
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13
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1, 1, 1, 1, 2, 2, 1, 3, 6, 4, 1, 4, 12, 16, 8, 1, 5, 20, 40, 40, 16, 1, 6, 30, 80, 120, 96, 32, 1, 7, 42, 140, 280, 336, 224, 64, 1, 8, 56, 224, 560, 896, 896, 512, 128, 1, 9, 72, 336, 1008, 2016, 2688, 2304, 1152, 256, 1, 10, 90, 480, 1680, 4032, 6720, 7680, 5760, 2560, 512
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OFFSET
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0,5
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COMMENTS
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Rows are associated with the expansions of (x^k/k!)exp(x)cosh(x) (leading zeros dropped). Rows include A011782, A057711, A080929, A082138, A080951, A082139, A082140, A082141. Columns are of the form 2^(k-1)C(n+k, k). Diagonals include A092246, A082143, A082144, A082145, A069720.
T(n, k) is also the number of idempotent order-preserving and order-decreasing partial transformations (of an n-chain) of width k (width(alpha)= |Dom(alpha)|). [From Abdullahi Umar, Oct 02 2008]
Read as a triangle this is A119468 with rows reversed. A119468 has e.g.f. exp(z*x)/(1-tanh(x)). - Peter Luschny, Aug 01 2012
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LINKS
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Table of n, a(n) for n=0..65.
Laradji, A. and Umar, A. Combinatorial results for semigroups of order-preserving partial transformations, Journal of Algebra 278, (2004), 342-359.
Laradji, A. and Umar, A. Combinatorial results for semigroups of order-decreasing partial transformations, J. Integer Seq. 7 (2004), 04.3.8
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FORMULA
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Square array defined by T(n, k)=(2^(n-1)+0^n/2)C(n + k, n)= Sum{k=0..n, C(n+k, k+j)C(k+j, k)(1+(-1)^j)/2 }
As an infinite lower triangular matrix, equals A007318 * A134309. - Gary W. Adamson, Oct 19 2007
O.g.f. for array read as a triangle: (1-x*(1+t))/((1-x)*(1-x*(1+2*t))) = 1 + x*(1+t) + x^2*(1+2*t+2*t^2) + x^3*(1+3*t+6*t^2+4*t^3) + .... - Peter Bala, Apr 26 2012
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EXAMPLE
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Rows begin
1 1 2 4 8 ...
1 2 6 16 40 ...
1 3 12 40 120 ...
1 4 20 80 280 ...
1 5 30 140 560 ...
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MATHEMATICA
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rows = 11; t[n_, k_] := 2^(n-1)*(n+k)!/(n!*k!); t[0, _] = 1; tkn = Table[ t[n, k], {k, 0, rows}, {n, 0, rows}]; Flatten[ Table[ tkn[[ n-k+1, k ]], {n, 1, rows}, {k, 1, n}]] (* From Jean-François Alcover, Jan 20 2012 *)
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PROG
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# (Sage)
def A082137_row(n) : # as a triangular array
var('z')
s = (exp(z*x)/(1-tanh(x))).series(x, n+2)
t = factorial(n)*s.coeff(x, n)
return [t.coefficient(z, n-k) for k in (0..n)]
for n in (0..7) : print A082137_row(n) # Peter Luschny, Aug 01 2012
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CROSSREFS
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Cf. A007318, A134309.
Sequence in context: A107230 A159830 A046726 * A091187 A065173 A098474
Adjacent sequences: A082134 A082135 A082136 * A082138 A082139 A082140
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KEYWORD
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easy,nonn,tabl
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AUTHOR
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Paul Barry, Apr 06 2003
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STATUS
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approved
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