A244421 Denominators of coefficient triangle for expansion of x^n in terms of polynomials Todd(k,x) = T(2*k+1, sqrt(x))/sqrt(x) (A084930), with the Chebyshev T-polynomials.

1, 4, 4, 8, 16, 16, 64, 64, 64, 64, 128, 64, 64, 256, 256, 512, 512, 1024, 1024, 1024, 1024, 1024, 4096, 4096, 2048, 2048, 4096, 4096, 16384, 16384, 16384, 16384, 16384, 16384, 16384, 16384, 32768, 8192, 8192, 16384, 16384, 8192, 8192, 65536, 65536, 131072, 131072, 65536, 65536, 65536, 65536, 262144, 262144, 262144, 262144, 262144, 524288, 524288, 131072, 131072, 1048576, 1048576, 524288, 524288, 1048576, 1048576

Offset: 0

Author

Wolfdieter Lang, Aug 04 2014

Keywords

• nonn
• easy
• frac
• tabl

Comments

For the numerator triangle see A244420, also for comments, and the rational entries R(n,m) of the lower triangular Riordan matrix denoted in standard fashion by ((2 - c(z/4))/(1-z), -1 + c(z/4)) with c the o.g.f. of the Catalan numbers A000108.

Examples

			The triangle a(n,m) begins:
  n\m   0     1     2     3     4     5     6 ...
  0:    1
  1:    4     4
  2:    8    16    16
  3:   64    64    64    64
  4:  128    64    64   256   256
  5:  512   512  1024  1024  1024  1024
  6: 1024  4096  4096  2048  2048  4096  4096
  ...
For more rows see the link.
For the rational triangle R(n,m) see the example section of A244420.
Expansion: x^3 = (35*Todd(0, x) + 21*Todd(1, x) + 7*Todd(2, x) + 1*Todd(3, x))/64 = (35 + 21*(-3+4*x) + 7*( 5-20*x+16*x^2) + (-7+56*x-112*x^2+64*x^3))/64. For the Todd polynomials see A084930.
		

Links

• Wolfdieter Lang, First rows of the triangle.

Crossrefs

Cf. A084930, A244420, A000108.

Formula

a(n,m) = denominator(R(n,m)) with the rationals Riordan matrix elements R(n,m)= [x^m]R(n,x), with the row polynomials R(n,x) generated by ((2 - c(z/4))/(1-z))/(1 - x*(-1 + c(z/4))) = 2*((1+x)*(z-1) + (1-x)*sqrt(1-z))/((1-z)*((1+x)^2*z - 4*x)), where c(x) is the o.g.f. of the Catalan numbers A000108.