one 435 three 17955 six 820 ten 153 Elapsed 0 seconds #!/usr/bin/perl -w use strict; my $time = time(); my %tri; # make hash of tiangular numbers 5 digits or less map{$tri{.5*$_*($_+1)}=1}1..446; ... ... # prove we are right! print "one $o$n$e " if defined $tri{"$o$n$e"}; print "three $t$h$r$e$e " if defined $tri{"$t$h$r$e$e"}; print "six $s$i$x " if defined $tri{"$s$i$x"}; print "ten $t$e$n\n" if defined $tri{"$t$e$n"}; $time = time()-$time; print "Elapsed $time seconds\n";