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%I #11 Jun 13 2018 09:12:55
%S 1,2,2,6,2,24,2,6,8,6,2,120,2,6,8,6,2,24,2,36,8,6,2,120,2,6,8,6,2,24,
%T 2,6,8,6,2,120,2,6,8,36,2,24,2,6,8,6,2,120,2,6,8,6,2,24,2,6,8,6,2,
%U 5040,2,6,8,6,2,24,2,6,8,6,2,120,2,6,8,6,2,24,2,36,8,6,2,120,2,6,8,6,2,24,2,6,8,6,2,120,2,6,8,36,2,24,2,6,8
%N a(n) = the product of number k <= n such that GCQ_A(n, k) = LCQ_A(n, k) = 0 (see definition in comments).
%C Definition of GCQ_A: The greatest common non-divisor of type A (GCQ_A) of two positive integers a and b (a<=b) is the largest positive non-divisor q of numbers a and b such that 1<=q<=a common to a and b; GCQ_A(a, b) = 0 if no such c exists.
%C GCQ_A(1, b) = GCQ_A(2, b) = 0 for b >=1. GCQ_A(a, b) = 0 or >= 2.
%C Definition of LCQ_A: The least common non-divisor of type A (LCQ_A) of two positive integers a and b (a<=b) is the least positive non-divisor q of numbers a and b such that 1<=q<=a common to a and b; LCQ_A(a, b) = 0 if no such c exists. LCQ_A(1, b) = LCQ_A(2, b) = 0 for b >=1. LCQ_A(a, b) = 0 or >= 2.
%H Antti Karttunen, <a href="/A196441/b196441.txt">Table of n, a(n) for n = 1..65537</a>
%F a(n) = A000142(n) / A196442(n).
%e For n = 6, a(6) = 24 because there are 4 cases k (k = 1, 2, 3, 4) with GCQ_A(6, k) = 0:
%e GCQ_A(6, 1) = 0, GCQ_A(6, 2) = 0, GCQ_A(6, 3) = 0, GCQ_A(6, 4) = 0, GCQ_A(6, 5) = 4, GCQ_A(6, 6) = 5. Product of such numbers k is 24.
%e Also there are 4 same cases k with LCQ_A(6, k) = 0:
%e LCQ_A(6, 1) = 0, LCQ_A(6, 2) = 0, LCQ_A(6, 3) = 0, LCQ_A(6, 4) = 0, LCQ_A(6, 5) = 4, LCQ_A(6, 6) = 4.
%o (PARI)
%o GCQ_A(a, b) = { forstep(m=min(a, b)-1, 2, -1, if(a%m && b%m, return(m))); 0; }; \\ From PARI-program in A196438.
%o A196441(n) = prod(k=1,n,if(2<=GCQ_A(n,k),1,k)); \\ _Antti Karttunen_, Jun 13 2018
%Y Cf. A196437, A196438, A196439, A196440, A196442, A196443, A196444.
%K nonn
%O 1,2
%A _Jaroslav Krizek_, Nov 26 2011
%E More terms from _Antti Karttunen_, Jun 13 2018
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