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A220423 Cubefree products of primorials, cf. A002110. 5
1, 2, 4, 6, 12, 30, 36, 60, 180, 210, 420, 900, 1260, 2310, 4620, 6300, 13860, 30030, 44100, 60060, 69300, 180180, 485100, 510510, 900900, 1021020, 3063060, 5336100, 6306300, 9699690, 15315300, 19399380, 58198140, 69369300, 107207100, 223092870, 290990700 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Suggested by a comment of Charles R Greathouse IV in A220264;

A212793(a(n)) = 1; A051903(a(n)) < 3;

A001221(a(n)) <= A001222(a(n)) <= 2*A001221(a(n));

A006530(a(n)) = A000040(A001221(a(n))).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

PROG

(Haskell)

import Data.Set (deleteFindMin, empty, fromList, union)

import qualified Data.Set as Set (null)

a220423 n = a220423_list !! (n-1)

a220423_list = f (splitAt 1 a002110_list) empty where

   f (us'@(u:_), vs'@(v:vs)) s

     | Set.null s || m > u

                 = f (v:us', vs) (s `union` (fromList $ map (* u) us'))

     | otherwise = m : f (us', vs') s'

     where (m, s') = deleteFindMin s

CROSSREFS

Subsequence of A004709, A073491; A220264 (subsequence).

Sequence in context: A095912 A143474 A261341 * A335068 A333931 A308618

Adjacent sequences:  A220420 A220421 A220422 * A220424 A220425 A220426

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Dec 14 2012

STATUS

approved

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Last modified June 13 22:55 EDT 2021. Contains 345016 sequences. (Running on oeis4.)