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%I #9 Sep 08 2018 22:16:11
%S 1,1,1,2,2,4,2,2,4,4,4,4,8,8,16,2,2,4,4,8,4,6,6,12,12,24,12,36,4,4,8,
%T 8,16,8,24,16,6,6,12,12,24,12,36,24,36,4,4,8,8,16,8,24,16,24,16,10,10,
%U 20,20,40,20,60,40,60,40,100,4,4,8,8,16,8,24,16,24,16,40,16
%N Triangle read by rows, A130207 * A000012 * A130207.
%C Left border = A000010.
%C Row sums = A143231: (1, 2, 8, 12, 40, 24, ...).
%C T(n,k) is the number of pairs (a,b), where 0 <= a < n, 0 <= b < k, gcd(a,n) != 1, and gcd(b,k) != 1. - _Joerg Arndt_, Jun 26 2011
%H Nathaniel Johnston, <a href="/A143230/b143230.txt">Rows 1..100, flattened</a>
%F Triangle read by rows, A130207 * A000012 * A130207, where A130207 = A000010 * 0^(n-k), 1 <= k <= n.
%F T(n,k) = phi(n) * phi(k), where phi(n) & phi(k) = Euler's totient function.
%e First few rows of the triangle:
%e 1;
%e 1, 1;
%e 2, 2, 4;
%e 2, 2, 4, 4;
%e 4, 4, 8, 8, 16;
%e 2, 2, 4, 4, 8, 4;
%e 6, 6, 12, 12, 24, 12, 36;
%e 4, 4, 8, 8, 16, 8, 24, 16;
%e 6, 6, 12, 12, 24, 12, 36, 24, 36;
%e ...
%e T(7,5) = 24 = phi(7) * phi(5) = 6 * 4.
%p with(numtheory): T := proc(n,k) return phi(n)*phi(k): end: seq(seq(T(n,k),k=1..n),n=1..12); # _Nathaniel Johnston_, Jun 26 2011
%Y Cf. A000010, A130207, A143231.
%K nonn,easy,tabl
%O 1,4
%A _Gary W. Adamson_, Jul 31 2008
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