Under the map of n -> sigma(n)-n = A001065(n) the primes all flush into 1, so there are two graphs, one with the 1, too crowded in some sense, http://www.strw.leidenuniv.nl/~mathar/progs/nToAlisigofn.ps and one without http://www.strw.leidenuniv.nl/~mathar/progs/nToAlisigofn2.ps Richard Mathar