A037866 a(n)=(number of digits <=3)-(number of digits >3) in base 7 representation of n.

1, 1, 1, -1, -1, -1, 2, 2, 2, 2, 0, 0, 0, 2, 2, 2, 2, 0, 0, 0, 2, 2, 2, 2, 0, 0, 0, 0, 0, 0, 0, -2, -2, -2, 0, 0, 0, 0, -2, -2, -2, 0, 0, 0, 0, -2, -2, -2, 3, 3, 3, 3, 1, 1, 1, 3, 3, 3, 3, 1, 1, 1, 3, 3, 3, 3, 1, 1, 1, 3, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, 1

Offset

1,7

Links

Table of n, a(n) for n=1..84.

Maple

A037866 := proc(n)
    a := 0 ;
    dgs := convert(n, base, 7);
    for i from 1 to nops(dgs) do
        if op(i, dgs)<=3 then
            a := a+1 ;
        else
            a := a-1 ;
        end if;
    end do:
    a ;
end proc:
seq(A037866(n), n=1..40) ; # R. J. Mathar, Jan 27 2025

Mathematica

d37[n_]:=Module[{d=IntegerDigits[n, 7]}, Count[d, _?(#<4&)]-Count[d, _?(#>3&)]]; Array[d37, 90, 0] (* Harvey P. Dale, Jun 28 2022 *)

Crossrefs

Sequence in context: A338505 A037867 A122879 * A394296 A333181 A306216

Adjacent sequences: A037863 A037864 A037865 * A037867 A037868 A037869

Keyword

base,sign

Author

Clark Kimberling

Status

approved