The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A308766 Numbers n such that the minimal mark in a length n sparse ruler is round(sqrt(9+12*n)/2) + 1. 3
 51, 59, 69, 113, 124, 125, 135, 136, 139, 149, 150, 151, 164, 165, 166, 179, 180, 181, 195, 196, 199, 209, 210, 211 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Other sparse rulers in the range length 1 to 213 have round(sqrt(9+12*n)/2) minimal marks. Minimal vertices in n-edge graceful graph = minimal marks in length n sparse ruler. Minimal marks can be derived from A004137 and using zero-count values in A103300. Conjecture: Minimal marks n - round(sqrt(9+12*n)/2) is always 0 or 1. LINKS P. Luschny, The Perfect Ruler Pyramid (1-101) P. Luschny, Perfect and Optimal Rulers CROSSREFS Cf. A046693, A004137, A103300, A103294. Sequence in context: A095525 A045805 A031410 * A039387 A043210 A043990 Adjacent sequences:  A308763 A308764 A308765 * A308767 A308768 A308769 KEYWORD nonn,hard,more AUTHOR Ed Pegg Jr, Jun 23 2019 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 18 15:30 EST 2020. Contains 332019 sequences. (Running on oeis4.)