A122425 - OEIS

%I #11 Feb 05 2015 12:15:18

%S 1,2,3,4,5,6,7,8,9,5,11,6,13,7,5,8,17,9,19,5,7,22,23,8,5,26,9,7,29,6,

%T 31,8,33,34,7,9,37,38,39,8,41,7,43,44,9,46,47,8,7,50,51,52,53,9,55,8,

%U 57,58,59,60,61,62,9,8,65,66,67,68,69,70,71,9,73,74,75,76,77,78,79,80,9,82,83

%N a(n) = lexicographically greatest divisor of n in decimal representation.

%C a(p) = p for primes p;

%C a(A122427(n)) = A122427(n), a(A122426(n)) < A122426(n);

%C a(A122428(n)) = A006530(A122428(n)).

%C a(n) = A254679(n,A000005(n)). - _Reinhard Zumkeller_, Feb 05 2015

%H Reinhard Zumkeller, <a href="/A122425/b122425.txt">Table of n, a(n) for n = 1..10000</a>

%e Divisors(24) = [1,2,3,4,6,8,12,24] --> [1,12,2,24,3,4,6,8],

%e therefore a(24) = 8;

%e divisors(42) = [1,2,3,6,7,14,21,42] --> [1,14,2,21,3,42,6,7],

%e therefore a(42) = 7.

%o (Haskell)

%o import import Data.List (maximumBy); Data.Ord (comparing)

%o a122425 = maximumBy (comparing show) . a027750_row

%o -- _Reinhard Zumkeller_, Feb 05 2015, Sep 15 2011

%Y Cf. A254679, A122426, A122427, A122428.

%K nonn,base

%O 1,2

%A _Reinhard Zumkeller_, Sep 04 2006