A306013 - OEIS

%I #4 Jun 26 2018 06:57:30

%S 1,2,3,4,5,7,8,9,11,13,16,17,19,23,25,27,29,31,32,36,37,41,43,47,49,

%T 53,59,61,64,67,71,73,79,81,83,89,97,100,144,196,225,324,400,441,484,

%U 576,676,784,1089,1156,1225,1296,1444,1521,1600,1936,2025,2116

%N Let P(m) be the product of unitary divisors of m; then a(n) is the position of P(n) when all the numbers P(m) are arranged in increasing order.

%C P(m) = A061537(m).

%t z = 100; r[n_] := Select[Divisors[n], GCD[#, n/#] == 1 &];

%t k[n_] := Length[r[n]];

%t Table[r[n], {n, 1, z}]

%t a[n_] := Apply[Times, r[n]]

%t u = Table[a[n], {n, 1, z}]

%t Sort[u]

%Y Cf. A077610, A229994, A229996, A305995, A306010, A306011, A306012.

%K nonn

%O 1,2

%A _Clark Kimberling_, Jun 24 2018