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A096091 Numbers n with property that largest number formed from digits of n (A004186(n)) is divisible by smallest number formed from digits of n (A004185(n)). 5

%I #32 Jul 14 2019 21:55:35

%S 1,2,3,4,5,6,7,8,9,10,11,20,22,30,33,40,44,50,55,60,66,70,77,80,88,90,

%T 99,100,101,105,108,110,111,150,180,200,202,220,222,300,303,330,333,

%U 400,404,405,440,444,450,500,501,504,505,510,540,550,555,600,606

%N Numbers n with property that largest number formed from digits of n (A004186(n)) is divisible by smallest number formed from digits of n (A004185(n)).

%C The number N = d*10^m*(10^k-1)/9 is a member for all m, k where 1 < d < 10, since the quotient is 10^m. E.g., for d = 7, m = 4, k = 8 we get N = 777777770000.

%C Conjecture: There are infinitely many terms besides these.

%C From _Jon E. Schoenfield_, Jul 26 2015: (Start)

%C Every number whose nonzero digits are all identical (e.g., 70770070777) is a term in the sequence (so the sequence is infinite). Also, if k is a term, then so is k*10 (hence, so is k*10^m for m >= 1). Removal of all terms that satisfy either of the above criteria still leaves an infinite number of terms, beginning with 105, 108, 150, 180, 405, 450, 501, 504, 510, 540, 801, 810, ... (see A260461).

%C If any integer k is a term, then so is every integer obtained by permuting the digits of k, except for some (not necessarily all) permutations beginning with 0. E.g., since 12000 is a member, so are all the other permutations of its digits that begin with 1 (i.e., 10002, 10020, and 10200), and all those that begin with 2 (i.e., 20001, 20010, 20100, and 21000), as well as the permutations that begin with a single 0 (which, after leading zeros are removed, reduce to 1002, 1020, 1200, 2001, 2010, and 2100), but not those that begin with more than one 0 (i.e., the sequence does not include 12, 21, 102, 120, 201, or 210). Aside from those terms whose nonzero digits are all identical, it appears that only a small number of patterns result from sorting the digits in increasing order (and discarding the zeros, which, of course, are all leading zeros): these "primitives" begin with 12, 15, 16, 18, 24, 25, 36, 45, 48, 125, ... (see A260462). (End)

%H Giovanni Resta, <a href="/A096091/b096091.txt">Table of n, a(n) for n = 1..10000</a>

%e 110 is a member as 110/011=10.

%p isA096091 := proc(n)

%p if modp( A004186(n),A004185(n))= 0 then

%p true;

%p else

%p false;

%p end if;

%p end proc:

%p for n from 1 to 1000 do

%p if isA096091(n) then

%p printf("%d,",n) ;

%p end if;

%p end do: # _R. J. Mathar_, Jul 26 2015

%t Select[Range[999], (d = Sort@ IntegerDigits@ #; Divisible@@ FromDigits/@ {Reverse@ d, d})&] (* _Giovanni Resta_, Jul 26 2015 *)

%Y Cf. A004185, A004186, A096089, A096090, A260461, A260462.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Jun 22 2004

%E Edited, corrected and extended by _Robert G. Wilson v_, Jun 23 2004

%E Entry revised by Editors of the OEIS, Jul 26 2015

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Last modified March 28 17:25 EDT 2024. Contains 371254 sequences. (Running on oeis4.)