A058441 -id:A058441 - cp's OEIS frontend

A058442 Squares composed of digits {0,4,8}, not ending with zero.

4, 484, 40804, 88804, 4008004, 4088484, 4848804, 400080004, 400880484, 484088004, 840884004, 40000800004, 40008800484, 40080840804, 40804808004, 48400880004, 400084080484, 4000008000004, 4000088000484, 4000808040804, 4080408080004, 4080488880484, 4840008800004

Offset: 1

Patrick De Geest, Nov 15 2000

Zhao Hui Du, Table of n, a(n) for n = 1..4000
Patrick De Geest, Index to related sequences.
Hisanori Mishima, Sporadic tridigital solutions.

Cf. A058441.

Select[FromDigits/@Tuples[{0,4,8},13],Mod[#,10]!=0&&IntegerQ[Sqrt[#]]&] (* Harvey P. Dale, Feb 14 2023 *)

a(n) = A058441(n)^2. - Elmo R. Oliveira, Jul 16 2025

A202170 Numbers k such that k^2 has only digits 0, 4 and 8.

Original entry on oeis.org

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

Offset: 1

M. F. Hasler, Dec 13 2011

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

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

Cf. A030097, A058441.

Includes 2*A136808.

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

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

Select[Sqrt[FromDigits[#]]&/@Tuples[{0,4,8},13],IntegerQ] (* Harvey P. Dale, Sep 08 2024 *)

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

More terms from Robert Israel, Jul 17 2018

A280828 Numbers k of the form 2*10^m + 2 such that 10^k + 9 is prime.

Original entry on oeis.org

4, 22, 202

Offset: 1

Sergey Pavlov, Jan 08 2017

Let k=2*10^(n-1)+2, then a(n)=10^k+9. For all k>4, k is a term of A058441.
The only known terms from A088275 (Numbers n such that 10^n + 9 is prime) that are of the form 2*10^j + 2 are 4, 22, and 202; given the lower bound given for that sequence's next term, a(4) >= 200002. - Jon E. Schoenfield, Jan 11 2017
For n<4, let k=a(n) and p=(10^k-9)/10^(k/2)+3=10^(k/2)+3, then p is prime. - Sergey Pavlov, Jan 13 2017

			For n=1, a(1)=4 and 10^4 + 9 is prime.

Cf. A043037, A058441, A088275, A144249, A205529.

Numbers k of the form 2*10^m + 2 such that 10^k + 9 is prime.

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A058442 Squares composed of digits {0,4,8}, not ending with zero.

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A202170 Numbers k such that k^2 has only digits 0, 4 and 8.

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A280828 Numbers k of the form 2*10^m + 2 such that 10^k + 9 is prime.

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