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

0,2

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

Prog

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

Crossrefs

Cf. A248128-A248130.

Cf. A102251.

Sequence in context: A317502 A213912 A070360 * A070346 A328754 A070345

Adjacent sequences: A248128 A248129 A248130 * A248132 A248133 A248134

Keyword

nonn,base

Author

M. F. Hasler, Oct 02 2014

Status

approved