function ab=sr_exp_abcd(dig,nofdig,N,a,b,c,d)
%SR_EXP_ABCD Recurrence coefficients for orthogonal polynomials
%relative to a four-parameter exponential weight function.
%   AB=SR_EXP_ABDC(DIG,N,A,B,C,D) generates in DIG-digit
%   arithmetic the Nx2 array AB of the first N recurrence
%   coefficients for polynomials orthogonal with respect to
%   the weight function w(x)=const*x^D*exp(-B/x^A-C*x^A) on 
%   [0,Inf], const=exp(1)/(3*sqrt(2*pi)), A>0, B>0, C>0, D real.

digits(dig); a=vpa(a); b=vpa(b); c=vpa(c); d=vpa(d);
mom=smom_exp_abcd(dig,N,a,b,c,d);
ab=schebyshev(dig,N,mom);
ab(1,2)=exp(vpa(1,dig))/(vpa(3,dig)*sqrt(vpa(2*pi,dig)))*ab(1,2);
ab=vpa(ab,nofdig);
