A225494 Numbers having only balanced prime factors, cf. A006562.

1, 5, 25, 53, 125, 157, 173, 211, 257, 263, 265, 373, 563, 593, 607, 625, 653, 733, 785, 865, 947, 977, 1055, 1103, 1123, 1187, 1223, 1285, 1315, 1325, 1367, 1511, 1747, 1753, 1865, 1907, 2287, 2417, 2677, 2809, 2815, 2903, 2963, 2965, 3035, 3125, 3265, 3307

Offset

1,2

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..5000

Formula

Multiplicative closure of A006562.

Prog

(Haskell)
import Data.Set (singleton, fromList, union, deleteFindMin)
a225494 n = a225494_list !! (n-1)
a225494_list = 1 : h (singleton p) ps [p] where
   (p:ps) = a006562_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

Cf. A225493 (strong), A225495 (weak), A225496 (non-balanced).

Sequence in context: A147184 A036133 A062671 * A139479 A078569 A044082

Adjacent sequences: A225491 A225492 A225493 * A225495 A225496 A225497

Keyword

nonn

Author

Reinhard Zumkeller, May 09 2013

Status

approved