## foo.erl
-module(foo).
-export([pythag/1]).
pythag(N) -> lists:usort(pythag_list(N)).
pythag_list(N) ->
    [ lists:usort([A, B, C]) ||
        A <- lists:seq(1, N),
        B <- lists:seq(1, N),
        C <- lists:seq(1, N),
        A + B + C =< N,
        A*A + B*B == C*C
    ].
## from the Erlang console...
c(foo).
foo:pythag(30).