%I #19 Dec 28 2023 19:00:51

%S 0,1,2,3,4,5,6,7,8,9,11,12,13,14,15,16,17,18,19,21,22,23,24,25,26,27,

%T 28,29,31,32,33,34,35,36,37,38,39,41,42,43,44,45,46,47,48,49,51,52,53,

%U 54,55,56,57,58,59,61,62,63,64,65,66,67,68,69,71,72,73,74,75,76,77,78,79,82

%N Numbers with property that no two consecutive base 9 digits are equal.

%H G. C. Greubel, <a href="/A043095/b043095.txt">Table of n, a(n) for n = 1..5000</a>

%p isA043095 := proc(n)

%p dgs := convert(n,base,9) ;

%p for i from 2 to nops(dgs) do

%p if op(i,dgs) = op(i-1,dgs) then

%p return false;

%p end if;

%p end do:

%p true ;

%p end proc:

%p A043095 := proc(n)

%p option remember;

%p if n =1 then

%p 0;

%p else

%p for a from procname(n-1)+1 do

%p if isA043095(a) then

%p return a;

%p end if;

%p end do;

%p end if;

%p end proc:

%p seq(A043095(n),n=1..120) ; # _R. J. Mathar_, Dec 28 2023

%t Select[Range[0,100],!MemberQ[Flatten[Differences/@Partition[ IntegerDigits[ #,9],2,1]],0]&] (* _Harvey P. Dale_, Apr 05 2014 *)

%o (PARI) isok(n) = {my(d = digits(n, 9)); for (i=2, #d, if (d[i] == d[i-1], return (0));); return (1);} \\ _Michel Marcus_, Oct 11 2017

%Y Cf. A000975 (base-2 analog), A031941 or A043089 (base-3 analog), A031942 or A043090 (base-4 analog), A031943 or A043091 (base-5 analog), A043092, ..., A043096 (base-6 through base-10 analog).

%K nonn,base

%O 1,3

%A _Clark Kimberling_