A043698 Numbers whose base-9 representation has an even number of runs.

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, 81, 90, 92, 93, 94, 95, 96, 97, 98, 101, 111, 121, 131, 141

Offset

1,1

Links

Table of n, a(n) for n=1..78.

Maple

isA043698 := proc(n)
    local dgs, runs, i ;
    dgs := convert(n, base, 9) ;
    runs :=1 ;
    for i from 2 to nops(dgs) do
        if op(i, dgs) <> op(i-1, dgs) then
            runs := runs+1 ;
        end if;
    end do:
    if type(runs, 'even') then
        true;
    else
        false;
    end if;
end proc:
A043698 := proc(n)
    option remember;
    local a;
    if n = 1 then
        9;
    else
        for a from procname(n-1)+1 do
            if isA043698(a) then
                return a ;
            end if;
        end do:
    end if
end proc:
seq(A043698(n), n=1..120) ; # R. J. Mathar, Feb 20 2023

Crossrefs

Sequence in context: A263772 A031954 A043631 * A043457 A202707 A031078

Adjacent sequences: A043695 A043696 A043697 * A043699 A043700 A043701

Keyword

nonn,base

Author

Clark Kimberling

Status

approved