A125886 -id:A125886 - cp's OEIS frontend

A125887 a(1) = 1, a(n) = smallest positive number b not among a(1)..a(n-1) and not a multiple of 10 such that the first digit of b = the last digit of a(n-1).

1, 11, 12, 21, 13, 31, 14, 41, 15, 51, 16, 61, 17, 71, 18, 81, 19, 91, 101, 102, 22, 23, 32, 24, 42, 25, 52, 26, 62, 27, 72, 28, 82, 29, 92, 201, 103, 33, 34, 43, 35, 53, 36, 63, 37, 73, 38, 83, 39, 93, 301, 104, 44, 45, 54, 46, 64, 47, 74, 48, 84, 49, 94, 401, 105, 55, 56, 65

Offset: 1

Zak Seidov, Dec 13 2006

A dyslexic person might have trouble distinguishing this sequence from A125886!

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

Cf. A125886.

Cf. A000030, A010879.

a125887 n = a125887_list !! (n-1)
a125887_list = 1 : f '1' (filter ((> 0) . (`mod` 10)) [11..]) where
   f d zs = y : f (last $ show y) (xs ++ ys) where
       (xs, y:ys) = span ((/= d) . head . show) zs
-- Reinhard Zumkeller, Jul 06 2011

A139079 Smallest number not yet in the sequence that contains the last digit of the previous term, with a(1) = 1.

Original entry on oeis.org

1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 101, 11, 12, 2, 21, 13, 3, 23, 31, 14, 4, 24, 34, 41, 15, 5, 25, 35, 45, 51, 16, 6, 26, 36, 46, 56, 61, 17, 7, 27, 37, 47, 57, 67, 71, 18, 8, 28, 38, 48, 58, 68, 78, 81, 19, 9, 29, 39, 49, 59, 69, 79, 89, 91, 102, 22, 32, 42, 52, 62, 72

Offset: 1

Franklin T. Adams-Watters, Jan 31 2009

This is a permutation of the positive integers.

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Cf. A076654, A125886.

a := [1] ; for n from 2 to 100 do ldig := op(-1,a) mod 10 ; for c from 1 do if c in a then ; else dgs := convert(c,base,10) ; if ldig in dgs then a := [op(a),c] ; break; fi; fi; od: od: print(a) ; # R. J. Mathar

s={1};Do[k=1;Until[ContainsAny[IntegerDigits[k],Take[IntegerDigits[s[[-1]]],-1]]&&!MemberQ[s,k],k++];AppendTo[s,k],{m,71}];s (* James C. McMahon, Jun 28 2025 *)

cp's OEIS Frontend

A125887 a(1) = 1, a(n) = smallest positive number b not among a(1)..a(n-1) and not a multiple of 10 such that the first digit of b = the last digit of a(n-1).

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