A125886 a(1) = 1, a(n) = smallest positive number b not among a(1)..a(n-1) such that the last digit of b = the first digit of a(n-1).

1, 11, 21, 12, 31, 13, 41, 14, 51, 15, 61, 16, 71, 17, 81, 18, 91, 19, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201, 22, 32, 23, 42, 24, 52, 25, 62, 26, 72, 27, 82, 28, 92, 29, 102, 211, 112, 221, 122, 231, 132, 241, 142, 251, 152, 261, 162, 271, 172, 281, 182

Offset: 1

Author

Zak Seidov, Dec 13 2006

Keywords

• base
• nonn
• look
• hear

Comments

A dyslexic person might have trouble distinguishing this sequence from A125887!

A010879(a(n+1)) = A000030(a(n)). - Reinhard Zumkeller, Aug 10 2014

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Hans Havermann, Graph of first 10000 terms

Crossrefs

Cf. A125887.

Cf. A000030, A010879.

Programs

Haskell

import Data.List (delete)
a125886 n = a125886_list !! (n-1)
a125886_list = 1 : f 1 [10..] where
   f u vs = g vs where
     g (w:ws) = if a010879 w == iu then w : f w (delete w vs) else g ws
     iu = a000030 u
-- Reinhard Zumkeller, Aug 10 2014

Mathematica

s={1}; fi=1; Do[Do[id=IntegerDigits[i]; la=id[[ -1]]; If[fi==la&&FreeQ[s,i],AppendTo[s,i]; fi=id[[1]]; Break[]],{i,11,10^5}],{999}]; s