The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A031959 Numbers with exactly three distinct base-7 digits. 2
51, 52, 53, 54, 55, 63, 66, 67, 68, 69, 70, 72, 74, 75, 76, 77, 79, 80, 82, 83, 84, 86, 87, 88, 90, 91, 93, 94, 95, 96, 99, 101, 102, 103, 104, 105, 108, 109, 110, 111, 119, 120, 123, 124, 125, 126, 127, 129, 131, 132, 133, 134, 136 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
MAPLE
f:= proc(d) uses combinat; local S, Res, A1, A1p, A2, x1, x2;
Res:= NULL:
for S in choose({$0..6}, 3) do
x1:= S[3]*(7^d-1)/6;
for A1 in powerset(d) minus {{}} do
if S[1]=0 and member(d, A1) then next fi;
x2:= x1 + (S[1]-S[3])*add(7^(j-1), j=A1);
A1p:= {$1..d} minus A1;
for A2 in powerset(A1p) minus {{}, A1p} do
Res:= Res, x2 + (S[2]-S[3])*add(7^(j-1), j=A2);
od
od
od;
sort([Res]);
end proc:
op(f(3)), op(f(4)); # Robert Israel, Oct 29 2018
MATHEMATICA
Select[Range[150], Length[Union[IntegerDigits[#, 7]]]==3&] (* Harvey P. Dale, Mar 29 2019 *)
CROSSREFS
Cf. A007093.
Sequence in context: A039932 A210183 A210086 * A144162 A169984 A042299
KEYWORD
nonn,base
AUTHOR
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 24 15:14 EDT 2024. Contains 372778 sequences. (Running on oeis4.)