|
|
A025613
|
|
Numbers of form 3^i*4^j, with i, j >= 0.
|
|
5
|
|
|
1, 3, 4, 9, 12, 16, 27, 36, 48, 64, 81, 108, 144, 192, 243, 256, 324, 432, 576, 729, 768, 972, 1024, 1296, 1728, 2187, 2304, 2916, 3072, 3888, 4096, 5184, 6561, 6912, 8748, 9216, 11664, 12288, 15552, 16384, 19683, 20736, 26244, 27648, 34992, 36864, 46656
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
Subsequence of 3-smooth numbers, cf. A003586.
|
|
LINKS
|
|
|
FORMULA
|
Sum_{n>=1} 1/a(n) = (3*4)/((3-1)*(4-1)) = 2. - Amiram Eldar, Sep 24 2020
|
|
MATHEMATICA
|
n = 10^5; Flatten[Table[3^i*4^j, {i, 0, Log[3, n]}, {j, 0, Log[4, n/3^i]}]] // Sort (* Amiram Eldar, Sep 24 2020 *)
|
|
PROG
|
(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a025613 n = a025613_list !! (n-1)
a025613_list = f $ singleton 1
where f s = m : (f $ insert (3*m) $ insert (4*m) s')
where (m, s') = deleteFindMin s
(PARI) list(lim)=my(v=List(), N); for(n=0, logint(lim\1, 3), N=3^n; while(N<=lim, listput(v, N); N<<=2)); Set(v) \\ Charles R Greathouse IV, Sep 10 2015
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|