

A108319


Numbers of the form (2^i)*(3^j)*(7^k), with i, j, k >= 0.


6



1, 2, 3, 4, 6, 7, 8, 9, 12, 14, 16, 18, 21, 24, 27, 28, 32, 36, 42, 48, 49, 54, 56, 63, 64, 72, 81, 84, 96, 98, 108, 112, 126, 128, 144, 147, 162, 168, 189, 192, 196, 216, 224, 243, 252, 256, 288, 294, 324, 336, 343, 378, 384, 392, 432, 441, 448, 486, 504, 512, 567
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Numbers m  42^e with integer e >= 0.  Michael De Vlieger, Aug 22 2019
Sum_{n>=1} 1/a(n) = (2*3*7)/((21)*(31)*(71)) = 7/2.  Amiram Eldar, Sep 24 2020


LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..10000


FORMULA

a(n) ~ exp((6*log(2)*log(3)*log(7)*n)^(1/3)) / sqrt(42).  Vaclav Kotesovec, Sep 23 2020


MATHEMATICA

With[{n = 567}, Sort@ Flatten@ Table[2^i * 3^j * 7^k, {i, 0, Log2@ n}, {j, 0, Log[3, n/2^i]}, {k, 0, Log[7, n/(2^i*3^j)]}]] (* Michael De Vlieger, Aug 22 2019 *)


CROSSREFS

Cf. A051037, A003586, A003591, A003594.
Sequence in context: A269804 A318400 A219174 * A177500 A018772 A134003
Adjacent sequences: A108316 A108317 A108318 * A108320 A108321 A108322


KEYWORD

nonn,easy


AUTHOR

Douglas Winston (douglas.winston(AT)srupc.com), Jun 30 2005


STATUS

approved



