cp's OEIS Frontend

A043095 Numbers with property that no two consecutive base 9 digits are equal.

%I A043095 #21 Aug 25 2025 11:20:55
%S A043095 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 A043095 28,29,31,32,33,34,35,36,37,38,39,41,42,43,44,45,46,47,48,49,51,52,53,
%U A043095 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 A043095 Numbers with property that no two consecutive base 9 digits are equal.
%H A043095 G. C. Greubel, <a href="/A043095/b043095.txt">Table of n, a(n) for n = 1..5000</a>
%p A043095 isA043095 := proc(n)
%p A043095     dgs := convert(n,base,9) ;
%p A043095     for i from 2 to nops(dgs) do
%p A043095         if op(i,dgs) = op(i-1,dgs) then
%p A043095             return false;
%p A043095         end if;
%p A043095     end do:
%p A043095     true ;
%p A043095 end proc:
%p A043095 A043095 := proc(n)
%p A043095     option remember;
%p A043095     if n =1 then
%p A043095         0;
%p A043095     else
%p A043095         for a from procname(n-1)+1 do
%p A043095             if isA043095(a) then
%p A043095                 return a;
%p A043095             end if;
%p A043095         end do;
%p A043095     end if;
%p A043095 end proc:
%p A043095 seq(A043095(n),n=1..120) ; # _R. J. Mathar_, Dec 28 2023
%t A043095 Select[Range[0,100],!MemberQ[Flatten[Differences/@Partition[ IntegerDigits[ #,9],2,1]],0]&] (* _Harvey P. Dale_, Apr 05 2014 *)
%o A043095 (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 A043095 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).
%Y A043095 Cf. A023804 (subsequence).
%K A043095 nonn,base,changed
%O A043095 1,3
%A A043095 _Clark Kimberling_