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URL: https://oeis.org/A115690

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A115690
Squares whose digit reversal is a powerful(1) number (A001694).
3
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
1,2
COMMENTS
If x is a member, then so is 100*x. - Robert Israel, Mar 16 2020
LINKS
FORMULA
Trivially, n^2 <= a(n) <= 100^(n-1). - Charles R Greathouse IV, Nov 01 2022
EXAMPLE
25281=159^2 and 18252=2^2*3^3*13^2 is powerful.
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
PROG
(PARI) is(k) = ispowerful(fromdigits(Vecrev(digits(k))));
select(is, vector(300, n, n^2)) \\ Michel Marcus, Nov 01 2022
CROSSREFS
Subsequence of A115656.
A033294 is a subsequence, and the main entry for this sequence.
Sequence in context: A335088 A247009 A245241 * A115689 A061457 A069707
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, Jan 31 2006
STATUS
approved