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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

Table of n, a(n) for n=1..24.

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

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