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Numbers that contain each decimal digit at least twice.
5

%I #13 Feb 25 2019 17:27:55

%S 10012233445566778899,10012233445566778989,10012233445566778998,

%T 10012233445566779889,10012233445566779898,10012233445566779988,

%U 10012233445566787899,10012233445566787989,10012233445566787998,10012233445566788799

%N Numbers that contain each decimal digit at least twice.

%C A subsequence of A171102. Contains A000079 o A215830, i.e., { 2^A215830(n); n=1,2,3... }, as a subsequence.

%C The first 17!/2^8 ~ 1.4e12 terms are of the form 10^19 + x, where x runs over all permutations of the digits 12233445566788799, up to 99887766554433221.

%H Robert Israel, <a href="/A215876/b215876.txt">Table of n, a(n) for n = 1..10000</a>

%p nextp:= proc(L) local m, i,j, r, rj;

%p for m from 2 while L[m-1] <= L[m] do od:

%p r:= 10:

%p for j from 1 to m-1 do

%p if L[j] > L[m] and L[j] < r then

%p r:= L[j]; rj:= j;

%p fi

%p od;

%p [ op(sort([seq(L[i],i={$1..m} minus {rj})],`>`)), r,seq(L[i],i=m+1..nops(L))]

%p end proc:

%p A[1]:= 10012233445566778899:

%p L:= convert(A[1],base,10):

%p for n from 2 to 100 do

%p L:= nextp(L);

%p A[n]:= add(L[i]*10^(i-1),i=1..nops(L));

%p od:

%p seq(A[i],i=1..100); # _Robert Israel_, Feb 25 2019

%o (PARI) is_A215876(N)={my(c=vector(10)); for(k=1,#N=Vecsmall(Str(N)), c[N[k]-47]++); vecmin(c)>1}

%K nonn,base,look

%O 1,1

%A _M. F. Hasler_, Aug 25 2012