

A005047


Minimal span of set of n elements with no 3term arithmetic progression.


10



0, 1, 3, 4, 8, 10, 12, 13, 19, 23, 25, 29, 31, 35, 39, 40, 50, 53, 57, 62, 70, 73, 81, 83, 91, 94, 99, 103, 110, 113, 120, 121, 136, 144, 149, 156, 162, 164, 168, 173, 193, 203, 208
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,3


COMMENTS

Length of shortest ruler with n marks, with no mark halfway between two other marks.  Christian Häggström, Nov 19 2018


REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, E10 (but beware of errors).


LINKS

Table of n, a(n) for n=1..43.
B. E. Brown and D. M. Gordon, On sequences without geometric progressions, Math. Comp. 65 (1996), no. 216, 17491754.
Index entries related to nonaveraging sequences


FORMULA

a(n) = A065825(n)  1.


EXAMPLE

Example for a(10) = 23: 0 1 4 6 10 15 17 18 22 23.


CROSSREFS

Cf. A065825.
Sequence in context: A191193 A047343 A155730 * A083317 A268514 A024514
Adjacent sequences: A005044 A005045 A005046 * A005048 A005049 A005050


KEYWORD

nonn,more


AUTHOR

N. J. A. Sloane.


EXTENSIONS

a(18)a(41) derived from A065825 by Rob Pratt, Jul 09 2015
a(1)a(2) prepended and a(42)a(43) derived from A065825 by Alois P. Heinz, Nov 18 2018


STATUS

approved



