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

 Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A319187 Number of pairwise coprime subsets of {1,...,n} of maximum cardinality (A036234). 1
 1, 1, 1, 2, 2, 2, 2, 3, 6, 6, 6, 6, 6, 6, 6, 8, 8, 8, 8, 8, 8, 8, 8, 8, 16, 16, 24, 24, 24, 24, 24, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 72, 72, 72, 72, 72, 72, 72, 72 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Two or more numbers are pairwise coprime if no pair of them has a common divisor > 1. A single number is not considered to be pairwise coprime unless it is equal to 1. LINKS FORMULA a(n) = Product_{p prime <= n} floor(log_p(n)). a(n) = A000005(A045948(n)). - Ridouane Oudra, Sep 02 2019 EXAMPLE The a(8) = 3 subsets are {1,2,3,5,7}, {1,3,4,5,7}, {1,3,5,7,8}. MATHEMATICA Table[Length[Select[Subsets[Range[n], {PrimePi[n]+1}], CoprimeQ@@#&]], {n, 24}] (* see A186974 for a faster program *) CROSSREFS Rightmost terms of A186974 and A320436. Run lengths are A053707. Cf. A015614, A036234, A051424, A085945, A186971, A186972, A186994, A276187, A303139, A320423, A320426. Cf. A000005, A045948. Sequence in context: A225941 A138705 A333528 * A248780 A213021 A078228 Adjacent sequences:  A319184 A319185 A319186 * A319188 A319189 A319190 KEYWORD nonn AUTHOR Gus Wiseman, Jan 09 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 December 2 18:08 EST 2020. Contains 338887 sequences. (Running on oeis4.)