# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a308766 Showing 1-1 of 1 %I A308766 #12 Jul 22 2021 02:09:39 %S A308766 51,59,69,113,124,125,135,136,139,149,150,151,164,165,166,179,180,181, %T A308766 195,196,199,209,210,211 %N A308766 Numbers k such that the minimal mark in a length k sparse ruler is round(sqrt(9 + 12*k)/2) + 1. %C A308766 Other sparse rulers in the range length 1 to 213 have round(sqrt(9 + 12*k)/2) minimal marks. %C A308766 Minimal vertices in k-edge graceful graph = minimal marks in length k sparse ruler. %C A308766 Minimal marks can be derived from A004137 and using zero-count values in A103300. %C A308766 Conjecture: Minimal marks k - round(sqrt(9 + 12*k)/2) is always 0 or 1. %H A308766 P. Luschny, The Perfect Ruler Pyramid (1-101) %H A308766 P. Luschny, Perfect and Optimal Rulers %Y A308766 Cf. A046693, A004137, A103300, A103294. %K A308766 nonn,hard,more %O A308766 1,1 %A A308766 _Ed Pegg Jr_, Jun 23 2019 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE