In order to obtain the spectrum of [and possibly other information about] strongly regular or distance-regular graphs, send email to aeb@cwi.nl with a subject line (in the header) Subject: exec drg followed by a body consisting of zero or more lines of the form drg d=D B[0],B[1],...,B[d-1]:C[1],...,C[d] where D is the diameter, and the B[i] and C[i] are the usual intersection numbers. An example: % mail aeb@cwi.nl Subject: exec drg drg d=2 14,12:1,4 drg d=2 20,18:1,6 drg d=2 30,20:1,12 drg d=4 45,44,36,5:1,9,40,45 . EOT % sleep 5 % mail "/usr/spool/mail/aeb": 25 messages 1 new 2 unread >N 25 aeb's.daemon@cwi.nl Fri Sep 10 19:05 50/1608 "Re: exec drg" ---t From aeb@cwi.nl Fri Sep 10 19:05:36 1993 Subject: Re: exec drg Reply-To: Andries.Brouwer@cwi.nl Delivered-By: aebmail Dear aeb@win.tue.nl (A.E. Brouwer), My programs, when called with your input drg d=2 14,12:1,4 drg d=2 20,18:1,6 drg d=2 30,20:1,12 drg d=4 45,44,36,5:1,9,40,45 produce the output given below. Best regards, Andries Brouwer - aeb@cwi.nl strongly regular graphs with n=57 and k=14 and lb=1 and mu=4 - n=57 k=14 lb=1 mu=4 r=2 s=-5 f=38 g=18 does not exist (WILBRINK & BROUWER) k=42 lb=31 mu=30 r=4 s=-3 f=18 g=38 does not exist (WILBRINK & BROUWER) ############ strongly regular graphs with n=81 and k=20 and lb=1 and mu=6 ! n=81 k=20 lb=1 mu=6 r=2 s=-7 f=60 g=20 [unique: Brouwer & Haemers] spg(3,10,1,6) - Cameron VO-(4,3) k=60 lb=45 mu=42 r=6 s=-3 f=20 g=60 ############ strongly regular graphs with n=81 and k=30 and lb=9 and mu=12 + n=81 k=30 lb=9 mu=12 r=3 s=-6 f=50 g=30 pg(6,6,2) - van Lint & Schrijver Interior points of a quadric (q=3,d=4,-) k=50 lb=31 mu=30 r=5 s=-4 f=30 g=50 delta(3,25,18,15)? ############ diam = 4 v = 486 = 1 + 45 + 220 + 198 + 22 i(45,44,36,5; 1,9,40,45) spectrum: 45**1 9**110 0**264 -9**110 -45**1 bipartite E.g. Koolen-Riebeek graph ############ ---