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.\" $OpenBSD: factorial.in,v 1.2 2017/07/04 14:53:27 schwarze Exp $
.Dd $Mdocdate$
.Dt FACTORIAL 1
.Os
.Sh NAME
.Nm factorial
.Nd factorial sequence
.Sh DESCRIPTION
.\" recursively calculate a single factorial
.de rfac
. ie \\$1>1 \{\
. No \\$1 *
. nr i \\$1-1
. rfac \\ni
. nr acc \\n[acc]*\\$1
. \}
. el .nr acc 1
..
.\" recursively print a sequence of factorials
.de fac
. No \\$1! =
. rfac \\$1
. if \\$1>1 1 =
. No \\n[acc]
. if \\$1 \{\
. br
. nr i \\$1-1
. fac \\ni
. \}
..
.\" main program
.fac 9
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