cp's OEIS Frontend

A190220 Numbers all of whose divisors are numbers whose decimal digits are in nonincreasing order.

%I A190220 #10 Feb 14 2019 00:49:00
%S A190220 1,2,3,4,5,6,7,8,9,10,11,20,21,22,31,33,40,41,43,44,53,55,61,62,63,66,
%T A190220 71,73,77,82,83,86,88,93,97,99,110,211,220,311,331,421,422,431,433,
%U A190220 440,443,511,521,541,622,631,633,641,643,653,661,662,733,743,751
%N A190220 Numbers all of whose divisors are numbers whose decimal digits are in nonincreasing order.
%C A190220 Subset of A009996. Superset of A028867, A190219 and A190217.
%H A190220 Nathaniel Johnston, <a href="/A190220/b190220.txt">Table of n, a(n) for n = 1..500</a>
%e A190220 Number 110 is in sequence because all divisors of 110 (1, 2, 5, 10, 11, 22, 55, 110) are numbers whose decimal digits are in nonincreasing order.
%p A190220 with(numtheory): A190220 := proc(n) option remember: local d, dd, i, j, k, m, poten: if(n=1)then return 1: fi: for k from procname(n-1)+1 do d:=divisors(k): poten:=1: for i from 1 to nops(d) do m:=-1: dd:=convert(d[i], base, 10): for j from 1 to nops(dd) do if(m<=dd[j])then m:=dd[j]: else poten:=0: break: fi: od: if(poten=0)then break:fi: od: if(poten=1)then return k: fi: od: end: seq(A190220(n), n=1..64); # _Nathaniel Johnston_, May 14 2011
%K A190220 nonn,base
%O A190220 1,2
%A A190220 _Jaroslav Krizek_, May 06 2011