This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A083408 #48 Mar 14 2025 20:04:24
%S A083408 63504,435600,6350400,7683984,16240900,25401600,43560000,66585600,
%T A083408 420332004,558471424,635040000,647804304,726949444,768398400,
%U A083408 782432784,1067328900,1624090000,1897473600,2341011456,2540160000,4356000000,6658560000,42033200400,50860172484,52587662400
%N A083408 Squares which can be expressed as the product of a number and its reversal in at least two different ways.
%C A083408 Union of A083406 and A083407. - _Lekraj Beedassy_, Apr 23 2006
%D A083408 S. S. Gupta, EPRNs, Science Today, Feb. 1987, India.
%H A083408 Chai Wah Wu, <a href="/A083408/b083408.txt">Table of n, a(n) for n = 1..2498</a> (n = 1..76 from Hans Havermann, n = 77..241 from David A. Corneth)
%H A083408 David A. Corneth, <a href="/A083408/a083408.gp.txt">Examples of factorizations of terms as described in Name.</a>
%H A083408 Shyam Sunder Gupta, <a href="http://www.shyamsundergupta.com/eporns.htm">EPRN Numbers</a>.
%H A083408 Shyam Sunder Gupta, <a href="https://doi.org/10.1007/978-981-97-2465-9_12">Equal Product of Reversible Numbers (EPRN)</a>, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 12, 353-365.
%e A083408 63504 = 252 * 252 = 144 * 441,
%e A083408 1239016098321 = 1113111 * 1113111 = 1022121 * 1212201, etc.
%e A083408 635040000 = 144 * 4410000 = 252 * 2520000 = 441 * 1440000. - _David A. Corneth_, Mar 22 2019
%o A083408 (PARI) is(n) = {if(!issquare(n), return(0)); my(d = divisors(n), t = 0); forstep(i = #d, #d \ 2 + 1, -1, revd = fromdigits(Vecrev(digits(d[i]))); if(revd * d[i] == n, t++; if(t >= 2, return(1)); ) ); 0 } \\ _David A. Corneth_, Mar 21 2019
%Y A083408 Cf. A062917, A066531, A083406 (even), A083407 (odd), A070760, A117281 (palindromic square roots), A206642 (non-palindromic square roots), A325150 (products in exactly two different ways), A307019 (products in exactly three different ways).
%K A083408 nonn,base
%O A083408 1,1
%A A083408 _Shyam Sunder Gupta_, Jun 07 2003
%E A083408 Corrected and extended by _Hans Havermann_, Feb 11 2012
%E A083408 a(21)-a(25) from _David A. Corneth_, Mar 21 2019
%E A083408 Definition corrected by _N. J. A. Sloane_, Aug 01 2019