code 35190;
  comment COMPUTATION OF I[A](X),   , I[N+A](X);
  procedure BESS IAPLUSN(A, X, N, IA); value A, X, N;
  integer N; real X, A; array IA;
  if X= 0 then 
  begin IA[0]:= if A= 0 then 1 else 0;
    for N:= N step -1 until 1 do IA[N]:= 0
  end else if A= 0 then 
  begin 
    BESS I(X, N, IA);
  end else if A= .5 then 
  begin real C;
    C:= .797 884 560 802 865 * SQRT(ABS(X)) * EXP (ABS (X));
    NONEXP SPHER BESSI(X, N, IA);
    for N:= N step -1 until 0 do IA[N]:= C*IA[N]
  end else 
  begin real EXPX;
    EXPX:= EXP(ABS(X));
    NONEXP BESS IAPLUSN(A, X, N, IA);
    for N:= N step -1 until 0 do IA[N]:= EXPX * IA[N]
  end BESS IAPLUSN;
        eop