A115690 Squares whose digit reversal is a powerful(1) number (A001694).

1, 4, 9, 100, 121, 144, 169, 400, 441, 484, 576, 676, 900, 961, 1089, 9801, 10000, 10201, 10404, 10609, 12100, 12321, 12544, 12769, 14400, 14641, 14884, 16900, 25281, 27225, 40000, 40401, 40804, 44100, 44521, 44944, 48400, 48841, 57600

Offset: 1

Author

Giovanni Resta, Jan 31 2006

Keywords

• nonn
• base

Comments

If x is a member, then so is 100*x. - Robert Israel, Mar 16 2020

Examples

			25281=159^2 and 18252=2^2*3^3*13^2 is powerful.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..1500

Crossrefs

Subsequence of A115656.

A033294 is a subsequence, and the main entry for this sequence.

Cf. A001694, A115689.

Programs

Maple

filter:= proc(n) local L,i,x;
  L:= convert(n,base,10);
  x:=add(L[-i]*10^(i-1),i=1..nops(L));
  andmap(t -> t[2]>=2, ifactors(x)[2]):
end proc:select(filter, [seq(i^2,i=1..10^4)]); # Robert Israel, Mar 16 2020

PARI

is(k) = ispowerful(fromdigits(Vecrev(digits(k))));
select(is, vector(300, n, n^2)) \\ Michel Marcus, Nov 01 2022

Formula

Trivially, n^2 <= a(n) <= 100^(n-1). - Charles R Greathouse IV, Nov 01 2022