# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a046028 Showing 1-1 of 1 %I A046028 #32 Jul 23 2024 10:53:36 %S A046028 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, %T A046028 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, %U A046028 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 %N A046028 Largest multiple prime factor of the n-th nonsquarefree number (A013929). %H A046028 Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 %H A046028 Eric Weisstein's World of Mathematics, Greatest Prime Factor. %H A046028 Eric Weisstein's World of Mathematics, Squareful. %F A046028 a(n) = A249740(A013929(n)). - _Amiram Eldar_, Feb 11 2021 %t A046028 Select[ FactorInteger[#]//Reverse, #[[2]]>1&, 1][[1, 1]]& /@ Select[ Range[300], !SquareFreeQ[#]& ] (* _Jean-François Alcover_, Nov 06 2012 *) %o A046028 (Haskell) %o A046028 a046028 n = a046028_list !! (n-1) %o A046028 a046028_list = f 1 where %o A046028 f x | null zs = f (x + 1) %o A046028 | otherwise = (fst $ head zs) : f (x + 1) %o A046028 where zs = reverse $ filter ((> 1) . snd) $ %o A046028 zip (a027748_row x) (a124010_row x) %o A046028 -- _Reinhard Zumkeller_, Dec 29 2012 %o A046028 (Python) %o A046028 from math import isqrt %o A046028 from sympy import mobius, factorint %o A046028 def A046028(n): %o A046028 def f(x): return n+sum(mobius(k)*(x//k**2) for k in range(1, isqrt(x)+1)) %o A046028 m, k = n, f(n) %o A046028 while m != k: %o A046028 m, k = k, f(k) %o A046028 s = factorint(m) %o A046028 return next(p for p in sorted(s,reverse=True) if s[p]>1) # _Chai Wah Wu_, Jul 22 2024 %Y A046028 Cf. A006530, A046027, A013929, A249740. %Y A046028 Cf. A027748, A124010, A212177. %K A046028 nonn,easy,nice %O A046028 1,1 %A A046028 _Eric W. Weisstein_ # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE