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Let b(k) be the k-th term of the flattened irregular array where the m-th row contains the positive divisors of m. (b(k) = A027750(k).) Let c(k) be the k-th term of the flattened irregular array where the m-th row contains the positive integers that are <= m and are coprime to m. (c(k) = A038566(k).) Then a(n) = gcd(b(n),c(n)).
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%I #9 Feb 07 2019 15:13:08

%S 1,1,1,1,1,1,1,2,1,1,1,1,1,2,1,1,1,2,1,1,1,1,1,1,2,5,1,1,1,1,1,3,1,2,

%T 3,1,1,1,1,1,1,1,1,5,1,1,1,2,1,4,1,1,1,2,3,2,1,6,1,1,1,1,1,1,1,2,1,1,

%U 1,1,1,2,1,1,1,1,1,1,1,1,1,2,3,4,1,1,1

%N Let b(k) be the k-th term of the flattened irregular array where the m-th row contains the positive divisors of m. (b(k) = A027750(k).) Let c(k) be the k-th term of the flattened irregular array where the m-th row contains the positive integers that are <= m and are coprime to m. (c(k) = A038566(k).) Then a(n) = gcd(b(n),c(n)).

%H Rémy Sigrist, <a href="/A132587/b132587.txt">Table of n, a(n) for n = 1..10000</a>

%H Rémy Sigrist, <a href="/A132587/a132587.gp.txt">PARI program for A132587</a>

%e A027750: 1, 1, 2, 1, 3, 1, 2, 4, 1, 5, 1, 2, 3, 6, ...

%e A038566: 1, 1, 1, 2, 1, 3, 1, 2, 3, 4, 1, 5, 1, 2, ...

%e The 14th terms of each list are 6 and 2.

%e So a(14) = gcd(6,2) = 2.

%o (PARI) See Links section.

%Y Cf. A132588, A132589, A027750, A038566.

%K nonn

%O 1,8

%A _Leroy Quet_, Aug 23 2007

%E More terms from _Rémy Sigrist_, Feb 07 2019