Algorithm 163: modified Hankel function
Henry E. Fettis · Communications of the ACM · 1963
integer procedure combination (m, n) ; value n; integer m, n; eommeut calculates the number of combinations of m things taken n at a tinm.If n is less than half of m, then the program calculates the combinations of m things taken m -n at a time which is the exact equivalent of m things taken n at a time; begin integer p, r, i; p:=m--n; ifn < p then beginp := n; n := m--pend; ifp = 0then begin r := 1; go to exit end; r:=n+l; fort := 2step 1 untilp do r := (r X (n+i))/i; exit: combination := r end combination