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

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

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base
• changed

Links

• G. C. Greubel, Table of n, a(n) for n = 1..5000

Crossrefs

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).

Cf. A023804 (subsequence).

Programs

Maple

isA043095 := proc(n)
    dgs := convert(n,base,9) ;
    for i from 2 to nops(dgs) do
        if op(i,dgs) = op(i-1,dgs) then
            return false;
        end if;
    end do:
    true ;
end proc:
A043095 := proc(n)
    option remember;
    if n =1 then
        0;
    else
        for a from procname(n-1)+1 do
            if isA043095(a) then
                return a;
            end if;
        end do;
    end if;
end proc:
seq(A043095(n),n=1..120) ; # R. J. Mathar, Dec 28 2023

Mathematica

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

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