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SUBROUTINE HEP

PURPOSE
   COMPUTE THE VALUES OF THE HERMITE POLYNOMIALS H(N,X)
   FOR ARGUMENT VALUE X AND ORDERS 0 UP TO N.

USAGE
   CALL HEP(Y,X,N)

DESCRIPTION OF PARAMETERS
   Y	 - RESULT VECTOR OF DIMENSION N+1 CONTAINING THE VALUES
	   OF HERMITE POLYNOMIALS OF ORDER 0 UP TO N
	   FOR GIVEN ARGUMENT X.
	   VALUES ARE ORDERED FROM LOW TO HIGH ORDER
   X	 - ARGUMENT OF HERMITE POLYNOMIAL
   N	 - ORDER OF HERMITE POLYNOMIAL

REMARKS
   N LESS THAN 0 IS TREATED AS IF N WERE 0

SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
   NONE

METHOD
   EVALUATION IS BASED ON THE RECURRENCE EQUATION FOR
   HERMITE POLYNOMIALS H(N,X)
   H(N+1,X)=2*(X*H(N,X)-N*H(N-1,X))
   WHERE THE FIRST TERM IN BRACKETS IS THE INDEX,
   THE SECOND IS THE ARGUMENT.
   STARTING VALUES ARE H(0,X)=1, H(1,X)=2*X.