OFFSET
0,3
COMMENTS
A coprime set of integers has no pair of elements for which (i,j)=0. Each element i in a subset contributes 2^(i-1) to the binary value for that subset. The integers missing from the sequence correspond to non-coprime subsets.
REFERENCES
Alan Sutcliffe, Divisors and Common Factors in Sets of Integers, awaiting publication.
LINKS
Ivan Neretin, Table of n, a(n) for n = 0..3232 (all terms up to 2^20)
EXAMPLE
a(11)=13 since the 11th coprime set counting from 0 is {4,3,1}, which maps onto 1101 binary = 13 decimal.
MATHEMATICA
a = {}; Do[set = Select[Range[Log2[n] + 1], Reverse[IntegerDigits[n, 2]][[#]] == 1 &]; If[Union@Flatten@Outer[If[#1 == #2, 1, GCD[#1, #2]] &, set, set] == {1}, AppendTo[a, n]], {n, 200}]; a (* Ivan Neretin, Aug 14 2015 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Alan Sutcliffe (alansut(AT)ntlworld.com), Aug 16 2003
STATUS
approved