>574,576
(x-a)^b をべき級数に展開できれば
　I_n = ∫_[0,∞) x^n･exp(-cx^2) dx = (1/2)[(1/c)^ν]∫_[0,∞) t^(ν-1)･exp(-t) dt
　　= (1/2)[(1/c)^(ν)]Γ(ν), ν≡(n+1)/2.
　I_0 = (1/2)√(π/c), I_{2m+1} = (1/2)[(1/c)^(m+1)] m!.
なんかを使えそうだが．．．