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A248131 Start with a(0) = 1, then a(n) = three times the n-th digit of the sequence.

%I A248131 #14 Oct 02 2014 22:51:48
%S A248131 1,3,9,27,6,21,18,6,3,3,24,18,9,9,6,12,3,24,27,27,18,3,6,9,6,12,6,21,
%T A248131 6,21,3,24,9,18,27,18,3,6,18,6,3,18,6,3,9,6,12,27,3,24,6,21,3,24,9,18,
%U A248131 3,24,18,9,3,24,18,9,27,18,3,6,6,21,9,6,12,18,6,3,9,6,12,27
%N A248131 Start with a(0) = 1, then a(n) = three times the n-th digit of the sequence.
%C A248131 A (more natural?) variant of A248128, using the same rule but the smallest nontrivial initial value a(0)=1 instead of 50. However, none of the digits 0 and 5 can appear in the sequence if they don't appear in a(0), which motivates A248128(0)=50. See A248153 for a variant using multiples of 7 instead of 3.
%C A248131 All terms a(n) with index n>0 are divisible by 3, the sequence a(n)/3 yields exactly the individual digits of this sequence.
%H A248131 Reinhard Zumkeller, <a href="/A248131/b248131.txt">Table of n, a(n) for n = 0..10000</a>
%o A248131 (PARI) a(n,s=1,d=[])={for(i=1,n,print1(s",");d=concat(d,if(s,digits(s)));s=3*d[1];d=vecextract(d,"^1"));s}
%o A248131 (Haskell)
%o A248131 a248131 n = a248131_list !! n
%o A248131 a248131_list = 1 : (map (* 3) $
%o A248131                concatMap (map (read . return) . show) a248131_list)
%o A248131 -- _Reinhard Zumkeller_, Oct 02 2014
%Y A248131 Cf. A248128-A248130.
%Y A248131 Cf. A102251.
%K A248131 nonn,base
%O A248131 0,2
%A A248131 _M. F. Hasler_, Oct 02 2014