

A038372


Largest subset of integers [ 1...n ] such that no member divides two others.


0



1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 10, 10, 11, 12, 12, 13, 14, 14, 15, 16, 16, 17, 18, 19, 20, 21, 21, 22, 22, 22, 23, 24, 24, 25, 26, 26, 27, 28, 28, 29, 30
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OFFSET

1,2


REFERENCES

R. K. Guy, Unsolved Problems Number Theory, B24.


LINKS

Table of n, a(n) for n=1..44.


FORMULA

a(n) >= ceiling(2n/3). For large n, 0.6725n <= a(n) <= 0.6736n (see Guy).


EXAMPLE

{6,817,1923,2529} is the largest set of positive integers <= 29 such that none of them divides two of the others. The cardinality of the set is 21, so a(29)=21.


CROSSREFS

Sequence in context: A032509 A322042 A004523 * A121930 A020909 A075357
Adjacent sequences: A038369 A038370 A038371 * A038373 A038374 A038375


KEYWORD

nonn


AUTHOR

John W. Layman


EXTENSIONS

More terms and additional comments from Jud McCranie, Jan 17 2001


STATUS

approved



