Inverse Laplace transform of non-symbolic function

I'm trying to compute the inverse Laplace transform of the function gam below

t = 0.7968;
r = 0.05;
C = 0.397;
G = 4.312;
M = 19.5587;
Y = 0.5839;

C = C*100^Y;
G = G/100;
M = M/100;
EQ =  C*t*gamma(2-Y)*(1/M^(2-Y) + 1/G^(2-Y));
I = @(nu,a,lambda) (2.*lambda).^(-nu/2).*gamma(nu).*Herm(-nu,a./sqrt(2*lambda));

phi = @(lambda) exp ( - C*t* (((2*lambda)./Y+M.^2./(Y*(1-Y))).*I(2-Y,M,lambda) + ...
    ((2*lambda)./Y+G.^2/(Y*(1-Y))).*I(2-Y,G,lambda) + ...
    (2*lambda*M)./(Y*(1-Y)).*I(3-Y,M,lambda)+ ...
    (2*lambda*G)./(Y*(1-Y)).*I(3-Y,G,lambda) - ...
    M.^Y./(Y*(1-Y)).*gamma(2-Y) - G.^Y./(Y*(1-Y)).*gamma(2-Y)));

gam = @(lambda) exp(-r*t).*((phi(lambda)-1)./lambda.^2 + EQ./lambda);
syms lambda K
price = ilaplace(gam,K);

where Herm is a function computing an infinite sum:

function x = Herm(nu,z)

S = 0; % Holds the sum
M = 10;
j = 0;
while M > (2*eps)
    M = gamma((j-nu)/2)*2.^((j-nu)/2)*(-z).^j./factorial(j);
    S = S + M;
    j = j + 1;
end
x = 1./(2*gamma(-nu))*S;

When running the code, I get the error: "Conversion to logical from sym is not possible.", and I guess it's because of the while loop in the function Herm since Matlab cannot compare symbolic variables with values. I don't know how I should work around this since I cannot apply the Gamma function on a symbolic variable and thereby not use symsum instead of my user defined Herm function?

My other problem is that I have tried to compute the inverse Laplace transform when Herm is equal to 1 just to test if it works, and the resulting function is

(8655406674580457*exp(23477544183654475070368399262999/2535301200456458802993406410752)*heaviside(K)*ilaplace(exp(- (13078573778032534235659040224658125*(2*lambda)^(5839/20000))/925226481841578934417406252023808 - (3983232481287751717700979741070630539400651704603*2^(5839/20000))/(11692013098647223345629478661730264157247460343808*lambda^(14161/20000)) - (3982073156105729051442022632207669983713730125349*2^(15839/20000))/(1387060907782069057605350303705368947727532032000*lambda^(4161/20000)))/lambda^2, lambda, K))/9007199254740992 - (8655406674580457*K)/9007199254740992 + 30121999757536443160652423468557/79228162514264337593543950336

That is, the resulting function is expressed as yet another inverse Laplace transform. Maybe something is wrong but I should be able to get some nice function since I am trying to replicate the results from this article

http://www.math.nyu.edu/research/carrp/papers/pdf/qvoptions5fs.pdf.

Thanks in advance.

[Jingyu Liu]

I have the same problem with you. Do you know how to do an inverse laplace transform with gamma function now? Thank you.