

A186994


Number of maximal subsets of {1, 2, ..., n} containing n and having pairwise coprime elements.


6



1, 1, 1, 1, 2, 1, 2, 1, 3, 2, 6, 1, 6, 2, 3, 2, 8, 1, 8, 2, 4, 2, 8, 1, 8, 4, 8, 6, 24, 1, 24, 6, 10, 6, 15, 2, 30, 6, 10, 3, 30, 2, 30, 6, 5, 6, 30, 2, 30, 6, 20, 12, 60, 4, 30, 6, 20, 12, 60, 2, 60, 12, 10, 12, 36, 4, 72, 12, 24, 3, 72, 4, 72, 12, 12, 12, 36
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OFFSET

1,5


COMMENTS

The elements of a maximal subset are 1, n, and powers of primes that have no common factor with n. The cardinalities of maximal subsets is A186971(n).


LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = Product_{p in Primes with p<n and GCD(n,p)=1} floor(log_p(n)).


EXAMPLE

a(5) = 2 because there are 2 maximal subsets of {1,2,3,4,5} containing 5 and having pairwise coprime elements: {1,2,3,5}, {1,3,4,5}.
a(9) = 3, the maximal subsets are {1,2,5,7,9}, {1,4,5,7,9}, {1,5,7,8,9}.


MAPLE

with(numtheory):
a:= n> mul(ilog[j](n), j={ithprime(i)$i=1..pi(n)} minus factorset(n)):
seq(a(n), n=1..200);


MATHEMATICA

a[n_] := Product[Log[p, n] // Floor, {p, Select[Range[n1], PrimeQ[#] && GCD[n, #] == 1&]}]; Table[a[n], {n, 1, 200}] (* JeanFrançois Alcover, Dec 09 2014, after Alois P. Heinz *)


CROSSREFS

Cf. A186971. Rightmost elements in rows of A186972.
Sequence in context: A269572 A029198 A029175 * A056889 A275761 A232396
Adjacent sequences: A186991 A186992 A186993 * A186995 A186996 A186997


KEYWORD

nonn,look,hear


AUTHOR

Alois P. Heinz, Mar 01 2011


STATUS

approved



