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A306013
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.
0
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, 53, 59, 61, 64, 67, 71, 73, 79, 81, 83, 89, 97, 100, 144, 196, 225, 324, 400, 441, 484, 576, 676, 784, 1089, 1156, 1225, 1296, 1444, 1521, 1600, 1936, 2025, 2116
OFFSET
1,2
COMMENTS
P(m) = A061537(m).
MATHEMATICA
z = 100; r[n_] := Select[Divisors[n], GCD[#, n/#] == 1 &];
k[n_] := Length[r[n]];
Table[r[n], {n, 1, z}]
a[n_] := Apply[Times, r[n]]
u = Table[a[n], {n, 1, z}]
Sort[u]
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jun 24 2018
STATUS
approved