While I wait for my approval from Seqfans (why did it take me so long to subscribe? I think it's because I was getting OEIS editor mail, and wrongly assumed it was the same thing) here's a sequence for which I would love to know the next couple of entries. What is the largest number of edges possessed by a graph that lacks 5-cycles? These graphs are, as usual, forbidden from having self-loops or multiple edges. A(1 .. 4) = 0, 1, 3, 6. I am pretty sure that A(5) = 7; in other words, you can't do better than K4 plus a whisker. If A(6) is anything bigger than 9 I will be extremely surprised. There are only seven sequences in OEIS matching 0, 1, 3, 6, 7, 9. I know that A(7) >= 12, and only three of the seven sequences satisfy that constraint. All the sequences except A047242 (0, 1, or 3 mod 6) are eliminated by the fact that A(1+3n) >= 6n; this number of vertices is achieved by n copies of K4 sharing one vertex. And finally, A(18) >= 36, which rules out A047242. My example here is a necklace of 6 copies of K4, arranged in a 6-cycle, each sharing one vertex with the next. So I am reasonably sure this sequence is missing from OEIS, but would like some confirmation from other funsters.