A037868 a(n)=(number of digits <=4)-(number of digits >4) in base 9 representation of n.

1, 1, 1, 1, -1, -1, -1, -1, 2, 2, 2, 2, 2, 0, 0, 0, 0, 2, 2, 2, 2, 2, 0, 0, 0, 0, 2, 2, 2, 2, 2, 0, 0, 0, 0, 2, 2, 2, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, -2, -2, -2, -2, 0, 0, 0, 0, 0, -2, -2, -2, -2, 0, 0, 0, 0, 0, -2, -2, -2, -2, 0, 0, 0, 0, 0, -2, -2, -2, -2

Offset

1,9

Links

Table of n, a(n) for n=1..80.

Maple

A037868 := proc(n)
    a := 0 ;
    dgs := convert(n, base, 9);
    for i from 1 to nops(dgs) do
        if op(i, dgs)<=4 then
            a := a+1 ;
        else
            a := a-1 ;
        end if;
    end do:
    a ;
end proc:
seq(A037868(n), n=1..40) ; # R. J. Mathar, Jan 27 2025

Mathematica

Table[Total[If[#<5, 1, -1]&/@IntegerDigits[n, 9]], {n, 0, 100}] (* Harvey P. Dale, Apr 06 2021 *)

Crossrefs

Sequence in context: A297038 A373096 A037869 * A173069 A363934 A059963

Adjacent sequences: A037865 A037866 A037867 * A037869 A037870 A037871

Keyword

base,sign

Author

Clark Kimberling

Status

approved