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A067581 a(1) = 1, a(n) = smallest integer not yet in the sequence with no digits in common with a(n-1). 9
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 22, 11, 20, 13, 24, 15, 23, 14, 25, 16, 27, 18, 26, 17, 28, 19, 30, 12, 33, 21, 34, 29, 31, 40, 32, 41, 35, 42, 36, 44, 37, 45, 38, 46, 39, 47, 50, 43, 51, 48, 52, 49, 53, 60, 54, 61, 55, 62, 57, 63, 58, 64, 59, 66, 70, 56, 71, 65, 72, 68, 73, 69 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

David W. Wilson has shown that the sequence contains every positive integer except those containing all the digits 1 through 9 (which obviously have no possible predecessor). Jun 04, 2002

a(A137857(n)) = A137857(n). - Reinhard Zumkeller, Feb 15 2008

LINKS

R. Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

a(14) = 13, since a(13) = 20 and all integers smaller than 13 have a digit in common with 20 or have already appeared in the sequence.

MATHEMATICA

f[s_List] := Block[{k = 1, id = IntegerDigits@ s[[ -1]]}, While[ MemberQ[s, k] || Intersection[id, IntegerDigits@k] != {}, k++ ]; Append[s, k]]; Nest[f, {1}, 71] [From Robert G. Wilson v, Apr 03 2009]

PROG

(Haskell)

import Data.List (delete, intersect); import Data.Function (on)

a067581 n = a067581_list !! (n-1)

a067581_list = 1 : f 1 [2..] where

   f u vs = v : f v (delete v vs)

     where v : _ = filter (null . (intersect `on` show) u) vs

-- Reinhard Zumkeller, Jul 01 2013

CROSSREFS

Cf. A136332.

Cf. A184992.

Cf. A239664.

Sequence in context: A138142 A085890 A134817 * A099469 A039112 A160015

Adjacent sequences:  A067578 A067579 A067580 * A067582 A067583 A067584

KEYWORD

easy,nonn,base,nice,look

AUTHOR

Ulrich Schimke (ulrschimke(AT)aol.com)

STATUS

approved

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Last modified July 23 03:59 EDT 2014. Contains 244850 sequences.