|
| |
|
|
A225493
|
|
Numbers having only strong prime factors, cf. A051634.
|
|
5
|
|
|
|
1, 11, 17, 29, 37, 41, 59, 67, 71, 79, 97, 101, 107, 121, 127, 137, 149, 163, 179, 187, 191, 197, 223, 227, 239, 251, 269, 277, 281, 289, 307, 311, 319, 331, 347, 367, 379, 397, 407, 419, 431, 439, 451, 457, 461, 479, 487, 493, 499, 521, 541, 557, 569, 587
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
LINKS
|
|
|
|
FORMULA
|
|
|
|
PROG
|
(Haskell)
import Data.Set (singleton, fromList, union, deleteFindMin)
a225493 n = a225493_list !! (n-1)
a225493_list = 1 : h (singleton p) ps [p] where
(p:ps) = a051634_list
h s xs'@(x:xs) ys
| m > x = h (s `union` (fromList $ map (* x) (1 : ys))) xs ys
| otherwise = m : h (s' `union` (fromList $ map (* m) ys')) xs' ys'
where ys' = m : ys; (m, s') = deleteFindMin s
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
|
|
|
STATUS
|
approved
|
| |
|
|
