This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A226319 #7 Jun 03 2013 14:48:01
%S A226319 3,21,21,21,675,4725,4725,98175,140175,543375,543375,23186625,
%T A226319 35026425,139264125,139264125,608679225,11553990525,87662479905,
%U A226319 87662479905,343947649815,2383529269275,4005262262925,4005262262925
%N A226319 a(n) is the smallest odd k > 1 such that k is a Niven number at least in all the bases from 1 to n.
%e A226319 a(4) = 21 because 21 is the smallest odd k > 1 which is Niven in bases 1 (trivial), 2, 3, and 4, being equal to (10101)_2, (210)_3 and (111)_4.
%t A226319 a[n_] := Block[{k=3}, n > 1 && While[Max@ Mod[k, Total /@ IntegerDigits[k, Range[2, n]]] > 0, k += 2]; k]; Array[a,9]
%Y A226319 Cf. A005349, A226169, A226320, A225427 (Niven in bases 1,...,n but not in base n+1).
%K A226319 nonn,base
%O A226319 1,1
%A A226319 _Giovanni Resta_, Jun 03 2013