OFFSET
1,3
COMMENTS
Most terms have a palindromic square; for the rare exceptions see A133901. - Klaus Brockhaus and Zak Seidov, Sep 29 2007
LINKS
Klaus Brockhaus, Table of n, a(n) for n = 1..360
EXAMPLE
33 and 99 are terms because 33^2=1089 => 9801=99^2 and 99^2=9801 => 1089=33^2.
MATHEMATICA
A128921=Select[Range[0, 100000], IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ #^2 ]]]]]&&FromDigits[Reverse[IntegerDigits[ # ]]]==#&]
PROG
(Python)
from sympy.ntheory.primetest import is_square
from itertools import chain, count, islice
def A128921_gen(): # generator of terms
return filter(lambda n:is_square(int(str(n**2)[::-1])), chain((0, ), chain.from_iterable(chain((int((s:=str(d))+s[-2::-1]) for d in range(10**l, 10**(l+1))), (int((s:=str(d))+s[::-1]) for d in range(10**l, 10**(l+1)))) for l in count(0))))
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Zak Seidov, Mar 02 2005, definition corrected Sep 16 2007
EXTENSIONS
More terms from Klaus Brockhaus, Sep 23 2007
STATUS
approved