Source code in the n/t/roff programming language

.nf
.ta T 2mR
.nr x 1 1
.nr y 2 1
.nr p 0
.while (\n[x] <= 12) \{\
.if (\n[x]<10) \0\c
\n[x]\c
.if (\n[x]=1)           \c
.while (\n[y] <= 12) \{\
.nr p \n[x]*\n[y]
.ie (\n[y]>=\n[x])      \n[p]   \c
.el             \c
.nr y +1
.\}
.br
.nr x +1
.nr y 1 1
.\}