A123904 a(n) = n-th integer from among those positive integers with an exponent of n in their prime-factorizations.

2, 9, 27, 81, 243, 704, 1664, 3840, 8704, 19456, 43008, 94208, 204800, 442368, 950272, 2031616, 4325376, 9175040, 19398656, 40894464, 85983232, 180355072, 377487360, 788529152, 1644167168, 3422552064, 7113539584, 14763950080

Offset

1,1

Links

Table of n, a(n) for n=1..28.

Example

The positive integers with an exponent 6 in their prime-factorizations are 64 = 2^6, 192 = 2^6 *3^1, 320 = 2^6 *5^1, 448 = 2^6 *7^1, 576 = 2^6 *3^2, 704 = 2^6 *11^1, 729 = 3^6,...etc. The 6th of these is 704, so a(6) = 704.

Mathematica

f[n_] := Min[3^n, 2^n*(2n - 1)]; Table[f[n], {n, 30}] (* Ray Chandler, Nov 23 2006 *)

Crossrefs

Sequence in context: A051746 A277240 A256233 * A327612 A019065 A115186

Adjacent sequences: A123901 A123902 A123903 * A123905 A123906 A123907

Keyword

nonn

Author

Leroy Quet, Nov 19 2006

Extensions

Extended by Ray Chandler, Nov 23 2006

Status

approved