%I
%S 1,0,1,2,0,1,0,6,0,1,12,0,12,0,1,0,60,0,20,0,1,120,0,180,0,30,0,1,0,
%T 840,0,420,0,42,0,1,1680,0,3360,0,840,0,56,0,1,0,15120,0,10080,0,1512,
%U 0,72,0,1,30240,0,75600,0,25200,0,2520,0,90,0,1,0,332640,0,277200,0
%N Triangle of coefficients for expressing x^n in terms of Hermite polynomials.
%C x^n = 1/2^n * Sum (a(n,k)*H_k(x)), k=0..n
%D M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 801. (Table 22.12)
%H M. Abramowitz and I. A. Stegun, eds., <a href="http://www.nrbook.com/abramowitz_and_stegun/">Handbook of Mathematical Functions</a>, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
%H <a href="/index/He#Hermite">Index entries for sequences related to Hermite polynomials</a>
%F E.g.f. (rel to x) A(x, y) = exp(x*y + x^2).
%F Sum_{ k>=0 } 2^k*k!*T(m, k)*T(n, k) = T(m+n, 0) = A067994(m+n) .  _Philippe Deléham_, Jul 02 2005
%F T(n, k) = 0 if nk is odd; T(n, k) = n!/(k!*((nk)/2)!) if nk is even .  _Philippe Deléham_, Jul 02 2005
%F T(n, k)=n!/(k!*2^((nk)/2)((nk)/2)!)*2^((n+k)/2)(1+(1)^(n+k))/2^(k+1) T(n, k)=A001498((n+k)/2, (nk)/2)2^((n+k)/2)(1+(1)^(n+k))/2^(k+1);  _Paul Barry_, Aug 28 2005
%F Exponential Riordan array (e^(x^2),x).  _Paul Barry_, Sep 12 2006
%F G.f.: 1/(1x*y2*x^2/(1x*y4*x^2/(1x*y6*x^2/(1x*y8*x^2/(1... (continued fraction). [From _Paul Barry_, Apr 10 2009]
%F The nth row entries may be obtained from D^n(exp(x*t)) evaluated at x = 0, where D is the operator sqrt(1+4*x)*d/dx.  Peter Bala, Dec 07 2011
%e 1; 0,1; 2,0,1; 0,6,0,1; 12,0,12,0,1; ...
%Y Row sums give A047974. Columns 02: A001813, A000407, A001814. Cf. A048854, A060821.
%K nonn,tabl
%O 0,4
%A _Christian G. Bower_, Jan 03 2002
