login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A202170 Numbers n such that n^2 has only digits 0, 4 and 8. 2
0, 2, 20, 22, 200, 202, 220, 298, 2000, 2002, 2020, 2022, 2200, 2202, 2980, 20000, 20002, 20020, 20022, 20200, 20220, 22000, 22002, 22020, 28998, 29800, 200000, 200002, 200020, 200022, 200200, 200202, 200220, 202000, 202002, 202200, 220000, 220002, 220020, 220200, 289980, 298000, 632522, 2000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

n = 2*m where m^2 has only digits 0, 1 and 2. - Robert Israel, Jul 17 2018

LINKS

Robert Israel, Table of n, a(n) for n = 1..204

MAPLE

Res:= NULL:

for x from 0 to 3^12 do

  L:= convert(x, base, 3);

  y:= add(L[i]*10^(i-1), i=1..nops(L));

  if issqr(y) then

    Res:= Res, 2*sqrt(y)

  fi

od:

Res; # Robert Israel, Jul 17 2018

PROG

(PARI) is_A202170(n)=!setminus(Set(Vec(Str(n^2))), Vec("048"))

(MAGMA) [ n: n in [0..10^6 by 2] | Set(Intseq(n^2)) subset [0, 4, 8] ]; // Bruno Berselli, Dec 19 2011

CROSSREFS

Cf. A030097, A058441.

Includes 2*A136808.

Sequence in context: A136885 A136909 A169965 * A136908 A196748 A144674

Adjacent sequences:  A202167 A202168 A202169 * A202171 A202172 A202173

KEYWORD

nonn,base

AUTHOR

M. F. Hasler, Dec 13 2011

EXTENSIONS

More terms from Robert Israel, Jul 17 2018

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 5 10:11 EST 2021. Contains 349543 sequences. (Running on oeis4.)