A046028 Largest multiple prime factor of the n-th nonsquarefree number (A013929).

2, 2, 3, 2, 2, 3, 2, 2, 5, 3, 2, 2, 3, 2, 2, 3, 2, 7, 5, 2, 3, 2, 2, 3, 2, 2, 3, 5, 2, 2, 3, 2, 2, 3, 2, 2, 7, 3, 5, 2, 3, 2, 2, 3, 2, 11, 2, 5, 3, 2, 2, 3, 2, 2, 3, 7, 2, 5, 2, 3, 2, 2, 3, 2, 2, 13, 3, 2, 5, 2, 3, 2, 2, 3, 2, 7, 3, 5, 2, 3, 2, 2, 3, 2, 2, 5, 2, 2, 3, 2, 2, 11, 3, 2, 7, 2, 5, 3, 2, 2, 3

Offset

1,1

Links

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

Eric Weisstein's World of Mathematics, Greatest Prime Factor.

Eric Weisstein's World of Mathematics, Squareful.

Formula

a(n) = A249740(A013929(n)). - Amiram Eldar, Feb 11 2021

Mathematica

Select[ FactorInteger[#]//Reverse, #[[2]]>1&, 1][[1, 1]]& /@ Select[ Range[300], !SquareFreeQ[#]& ] (* Jean-François Alcover, Nov 06 2012 *)

Prog

(Haskell)
a046028 n = a046028_list !! (n-1)
a046028_list = f 1 where
   f x | null zs   = f (x + 1)
       | otherwise = (fst $ head zs) : f (x + 1)
       where zs = reverse $ filter ((> 1) . snd) $
                  zip (a027748_row x) (a124010_row x)
-- Reinhard Zumkeller, Dec 29 2012

Crossrefs

Cf. A006530, A046027, A013929, A249740.

Cf. A027748, A124010, A212177.

Sequence in context: A130285 A046027 A283671 * A330406 A125954 A122443

Adjacent sequences: A046025 A046026 A046027 * A046029 A046030 A046031

Keyword

nonn,easy,nice

Author

Eric W. Weisstein

Status

approved