+0 from me as well; agreed with everything that Tim said (except that I've never had a need for the Carmichael function; my RSA implementations do the inefficient thing based on (p-1)(q-1)).

This is somewhat reminiscent of comb and perm: lcm is often taught as a natural counterpart to gcd, so despite the fact that it's less fundamental and has less utility, people often expect to see the two together.

@Ananthakrishnan: do you want to put together a PR? I'll commit to reviewing it if you do.