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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 (list; graph; refs; listen; history; text; internal format)
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[n-1], PrimeQ[#] && GCD[n, #] == 1&]}]; Table[a[n], {n, 1, 200}] (* Jean-Fran├žois 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

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Last modified February 28 08:28 EST 2020. Contains 332323 sequences. (Running on oeis4.)