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

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, 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, 3, 24, 18, 9, 3, 24, 18, 9, 27, 18, 3, 6, 6, 21, 9, 6, 12, 18, 6, 3, 9, 6, 12, 27

Offset: 0

Author

M. F. Hasler, Oct 02 2014

Keywords

• nonn
• base

Comments

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.

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.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A248128-A248130.

Cf. A102251.

Programs

Haskell

a248131 n = a248131_list !! n
a248131_list = 1 : (map (* 3) $
               concatMap (map (read . return) . show) a248131_list)
-- Reinhard Zumkeller, Oct 02 2014

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}