A331285 a(n) is the index of the first occurrence of n in A331284.

1, 8, 27, 108, 180, 396, 672, 1056, 1372, 1760, 2352, 3087, 3696, 3744, 4896, 5733, 7497, 9724, 11907, 13600, 15200, 18513, 19773, 23940, 24752, 28917, 32319, 33534, 42282, 45472, 47500, 52668, 55890, 59976, 66048, 74240, 77792, 81144, 86944, 100035, 105248, 109368, 122825, 127908, 134368, 144648, 156325, 168948, 175770

Offset: 1

Author

Antti Karttunen, Jan 14 2020

Keywords

• nonn

Comments

Also positions of records in A331284.

a(n) is the least k such that in range 1 .. k of A329605 (equally: in A329606[1..k]) there can be found exactly n occurrences of some term. In A329605 these "champion terms" are A329605(a(n)): 1, 4, 16, 24, 48, 192, 96, 192, 384, 288, 288, 576, 576, 576, 1152, 2304, 4608, 9216, 576, 2304, ..., that appear all to be 3-smooth numbers (in A003586).

For example, a(5)=180 and 48 is the first term in A329605 to occur for five times, as A329605(22) = A329605(42) = A329605(75) = A329605(112) = A329605(180) = 48.

Crossrefs

Cf. A331284 (a left inverse).

Cf. A003586, A329605, A329606.

Formula

A331284(a(n)) = n for all n >= 1.