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A185348 Number of ordered quadruples of distinct pairwise coprime positive integers with largest element n; also first differences of A015623. 4

%I

%S 0,0,0,0,2,0,8,4,10,2,42,4,79,16,25,36,183,20,277,50,100,70,491,56,

%T 399,139,340,146,1016,56,1285,398,493,342,706,184,2150,501,807,363,

%U 2968,210,3522,775,935,904,4620,508,3732,842,2011,1255,6684,728,3355,1304,2785,1877,9141,546

%N Number of ordered quadruples of distinct pairwise coprime positive integers with largest element n; also first differences of A015623.

%H Alois P. Heinz, <a href="/A185348/b185348.txt">Table of n, a(n) for n = 1..1000</a>

%e a(4) = 0 because there is only one ordered quadruple of distinct positive integers with largest element 4, (1,2,3,4), but the elements are not pairwise coprime, 2 and 4 have a common factor >1.

%e a(8) = 4 because there are only four ordered quadruples of distinct pairwise coprime positive integers with largest element 8: (1,3,5,8), (1,3,7,8), (1,5,7,8), (3,5,7,8).

%Y Cf. A015623, A185953. Column 4 of triangle A186972.

%K nonn

%O 1,5

%A _Alois P. Heinz_, Feb 15 2011

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Last modified September 26 08:11 EDT 2021. Contains 347664 sequences. (Running on oeis4.)