A215876 Numbers that contain each decimal digit at least twice.

10012233445566778899, 10012233445566778989, 10012233445566778998, 10012233445566779889, 10012233445566779898, 10012233445566779988, 10012233445566787899, 10012233445566787989, 10012233445566787998, 10012233445566788799

Offset

1,1

Comments

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

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.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

nextp:= proc(L) local m, i, j, r, rj;
for m from 2 while L[m-1] <= L[m] do od:
r:= 10:
for j from 1 to m-1 do
   if L[j] > L[m] and L[j] < r then
      r:= L[j]; rj:= j;
   fi
od;
[ op(sort([seq(L[i], i={$1..m} minus {rj})], `>`)), r, seq(L[i], i=m+1..nops(L))]
end proc:
A[1]:= 10012233445566778899:
L:= convert(A[1], base, 10):
for n from 2 to 100 do
  L:= nextp(L);
  A[n]:= add(L[i]*10^(i-1), i=1..nops(L));
od:
seq(A[i], i=1..100); # Robert Israel, Feb 25 2019

Prog

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

Crossrefs

Sequence in context: A222534 A071759 A364363 * A095435 A155960 A266961

Adjacent sequences: A215873 A215874 A215875 * A215877 A215878 A215879

Keyword

nonn,base,look

Author

M. F. Hasler, Aug 25 2012

Status

approved