November 11, 1965

Mrs. Margaret Wightman
443 Echo Drive

Ottawa, Ontario

Canada

Dear Peggy:

I had a gote about your possible job as a programmer at Ottava and hope
this worked out to your satisfaction.

Julie and Bill have a pretty good hold on the programs you started and there
is no loss of continuity. The main challenges may come when the programs
are translated into PL-I for the /360 system. (You might be interested to
hear what we are planning on this - per enclosure. Dr. McCarthy's PDP-6 is
not coming to the medical school, but after some more delay ACME will more
than take its place.)

I did want to tell you that the list of 8 triangle-face polyhedra you
generated matches Grace's test perfectly, after the gauche figures are ex-
tracted. Bill put up a good program to do this. But your generator did

let through some 2-connected forms, not with any serious consequences. (These
were the unions of triangle-free polyhedra. )

Do you remember all the combinatorial tricks for generating permitations
systematically? Finally there is a coherent treatment of them, Lehmer's
chapter in a book you definitely should know about: Beckenback, E. E. (ed.)
"Applied Combinatorial Mathematics", Wiley, 1964.

Best regards,

Joshua Lederberg
Professor of Genetics