A108238 - OEIS

%I #9 Sep 26 2020 03:57:09

%S 1,7,12,49,84,144,343,588,1008,1728,2401,4116,7056,12096,16807,20736,

%T 28812,49392,84672,117649,145152,201684,248832,345744,592704,823543,

%U 1016064,1411788,1741824,2420208,2985984,4148928,5764801,7112448

%N Numbers of the form (7^i)*(12^j), with i, j >= 0.

%H Amiram Eldar, <a href="/A108238/b108238.txt">Table of n, a(n) for n = 1..10000</a>

%F Sum_{n>=1} 1/a(n) = (7*12)/((7-1)*(12-1)) = 14/11. - _Amiram Eldar_, Sep 26 2020

%F a(n) ~ exp(sqrt(2*log(7)*log(12)*n)) / sqrt(84). - _Vaclav Kotesovec_, Sep 26 2020

%t Take[7^#[[1]]*12^#[[2]]&/@Tuples[Range[0,10],2]//Union,40] (* _Harvey P. Dale_, Mar 05 2017 *)

%t n = 10^6; Flatten[Table[7^i*12^j, {i, 0, Log[7, n]}, {j, 0, Log[12, n/7^i]}]] // Sort (* _Amiram Eldar_, Sep 26 2020 *)

%Y Cf. A036566, A025631, A025632, A003599, A108056, A108201, A064476.

%K nonn,easy

%O 1,2

%A Douglas Winston (douglas.winston(AT)srupc.com), Jun 17 2005