A261787 a(n) is the smallest nonzero number that is not a substring of n in ternary representation.

1, 2, 1, 2, 2, 3, 1, 3, 1, 2, 2, 4, 2, 2, 3, 3, 3, 3, 1, 3, 1, 4, 3, 3, 1, 3, 1, 2, 2, 4, 2, 2, 4, 4, 4, 4, 2, 2, 5, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 3, 3, 3, 3, 3, 1, 3, 1, 4, 3, 3, 1, 3, 1, 4, 4, 4, 5, 3, 3, 3, 3, 3, 1, 3, 1, 4, 3, 3, 1, 3, 1, 2, 2, 4, 2, 2

Offset: 0

Author

Reinhard Zumkeller, Sep 01 2015

Keywords

• nonn
• base

Links

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

Crossrefs

Cf. A007089, A030341, A261789, A261786, A261461, A261794.

Programs

Haskell

import Data.List (isInfixOf)
a261787 x = f $ tail a030341_tabf where
   f (cs:css) = if isInfixOf cs (a030341_row x)
                   then f css else foldr (\d v -> 3 * v + d) 0 cs

PARI

ts(n) = Str(fromdigits(digits(n, 3)));
a(n) = my(s=ts(n), k=1); while (#strsplit(s, ts(k)) != 1, k++); k; \\ Michel Marcus, Feb 05 2022

Formula

A261789(n) = a(A261786(n)).