A186985 - OEIS

%I #6 Mar 30 2012 17:37:34

%S 8,8,8,8,89,90,164,168,238,244,1300,1301,4941,5734,6132,6379,7000,

%T 7089,22019,22975,24637,25150,67393,67678,160771,167602,174367,182152,

%U 395833,401344,563893,577192,621709,646954,1280587,1297318,1442533,1478536

%N Number of 9-element subsets of {1, 2, ..., n} having pairwise coprime elements.

%H Alois P. Heinz, <a href="/A186985/b186985.txt">Table of n, a(n) for n = 19..200</a>

%e a(19) = 8 because there are 8 9-element subsets of {1, 2, ..., 19} having pairwise coprime elements: {1,3,4,5,7,11,13,17,19}, {1,3,5,7,8,11,13,17,19}, {1,3,5,7,11,13,16,17,19}, {1,2,3,5,7,11,13,17,19}, {1,4,5,7,9,11,13,17,19}, {1,2,5,7,9,11,13,17,19}, {1,5,7,8,9,11,13,17,19}, {1,5,7,9,11,13,16,17,19}.

%Y Column 9 of triangle A186974. Partial sums of A186980.

%K nonn

%O 19,1

%A _Alois P. Heinz_, Mar 02 2011