[math-fun] Permutations

a) If you are generating a sequence of permutations by using swaps, successive permutations will be odd and even. b) If you know the number of loops in a permutation, it's easy to calculate odd or even-ness. c) vintage: I know the MIT crowd were generating permutations using swaps c. 1966; Gosper might be able to establish an earlier date. Rich