Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #12 Nov 01 2019 10:28:06
%S 2,9,27,81,243,704,1664,3840,8704,19456,43008,94208,204800,442368,
%T 950272,2031616,4325376,9175040,19398656,40894464,85983232,180355072,
%U 377487360,788529152,1644167168,3422552064,7113539584,14763950080
%N a(n) = n-th integer from among those positive integers with an exponent of n in their prime-factorizations.
%e 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.
%t f[n_] := Min[3^n, 2^n*(2n - 1)];Table[f[n], {n, 30}] (* _Ray Chandler_, Nov 23 2006 *)
%K nonn
%O 1,1
%A _Leroy Quet_, Nov 19 2006
%E Extended by _Ray Chandler_, Nov 23 2006