#!/usr/local/src/cmd/calc/calc -S
#
# mersenne - print the value of a mersenne number
#
# Copyright (C) 1999  Landon Curt Noll
#
# Calc is open software; you can redistribute it and/or modify it under
# the terms of the version 2.1 of the GNU Lesser General Public License
# as published by the Free Software Foundation.
#
# Calc is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE.	See the GNU Lesser General
# Public License for more details.
#
# A copy of version 2.1 of the GNU Lesser General Public License is
# distributed with calc under the filename COPYING-LGPL.  You should have
# received a copy with calc; if not, write to Free Software Foundation, Inc.
# 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
#
# @(#) $Revision: 29.1 $
# @(#) $Id: mersenne.calc,v 29.1 1999/12/14 09:15:35 chongo Exp $
# @(#) $Source: /usr/local/src/cmd/calc/cscript/RCS/mersenne.calc,v $
#
# Under source code control:	1999/11/30 00:09:01;
# File existed as early as:	1999
#
# chongo <was here> /\oo/\	http://reality.sgi.com/chongo/
# Share and enjoy!  :-) http://reality.sgi.com/chongo/tech/comp/calc/

# usage:
#	mersenne exp


/*
 * parse args
 */
if (argv() != 1) {
	/* we include the name of this script in the error message */
	fprintf(files(2), "usage: %s exp\n", config("program"));
	abort "wrong number of args";
}

/*
 * print the decimal value of 2^n-1
 */
print "2^": argv(0) : "-1 =", 2^eval(argv(0))-1;