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%I #34 Jun 07 2023 04:44:13
%S 1,4,9,121,144,169,441,484,676,961,1089,9801,10201,10404,10609,12321,
%T 12544,12769,14641,14884,40401,40804,44521,44944,48841,69696,90601,
%U 94249,96721,698896,1002001,1004004,1006009,1022121,1024144,1026169
%N Squares which when written backwards remain square (final 0's excluded).
%C Of this sequence's first 10000 terms, only nine have an even number of digits; see A354256.
%H Jon E. Schoenfield, <a href="/A033294/b033294.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Reinhard Zumkeller)
%H <a href="/index/Sq#sqrev">Index entry for sequences related to reversing digits of squares</a>
%e 144 = 12 * 12 is a term because 441 = 21 * 21.
%t Select[Range[1100]^2,Mod[#,10]!=0&&IntegerQ[Sqrt[FromDigits[Reverse[ IntegerDigits[ #]]]]]&] (* _Harvey P. Dale_, Oct 28 2013 *)
%o (Haskell)
%o a033294 n = a033294_list !! (n-1)
%o a033294_list = filter chi a000290_list where
%o chi m = m `mod` 10 > 0 && head ds `elem` [1,4,5,6,9] &&
%o a010052 (foldl (\v d -> 10 * v + d) 0 ds) == 1 where
%o ds = unfoldr
%o (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 10) m
%o -- _Reinhard Zumkeller_, Jan 19 2012
%o (Python)
%o from math import isqrt
%o from itertools import count, islice
%o def sqr(n): return isqrt(n)**2 == n
%o def agen():
%o yield from (k*k for k in count(1) if k%10 and sqr(int(str(k*k)[::-1])))
%o print(list(islice(agen(), 36))) # _Michael S. Branicky_, May 21 2022
%Y Subsequence of A115690.
%Y Cf. A007488, A007500, A061457, A354256.
%K base,nonn
%O 1,2
%A _Jeff Burch_
%E More terms from _Erich Friedman_
%E Initial 0 removed and offset changed by _Reinhard Zumkeller_, Jan 19 2012
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