cp's OEIS Frontend

A289140 Positive numbers k such that rev(k)^2 + rev(k^2) is a square, where rev(n) = A004086(n) is the digital reverse of n.

%I A289140 #11 Jun 29 2017 12:18:24
%S A289140 998586,3632658,9985860,36326580,74471091,99664458,99858600,363265800,
%T A289140 634826115,743193501,744710910,756335085,759317343,996644580,
%U A289140 998586000,3632658000,6348261150,7177621788,7431935010,7447109100,7563350850,7593173430,9966445800
%N A289140 Positive numbers k such that rev(k)^2 + rev(k^2) is a square, where rev(n) = A004086(n) is the digital reverse of n.
%C A289140 Every term must be a multiple of 3.
%e A289140 998586 is a term since rev(998586^2) + 685899^2 = 1079100^2.
%t A289140 rev[n_] := FromDigits@ Reverse@ IntegerDigits@ n; Parallelize@ Select[3 Range[4 10^6], IntegerQ@ Sqrt[rev[#^2] + rev[#]^2] &]
%o A289140 (PARI) isok(n) = issquare(fromdigits(Vecrev(digits(n)))^2 + fromdigits(Vecrev(digits(n^2)))); \\ _Michel Marcus_, Jun 29 2017
%Y A289140 Cf. A004086, A061230, A061231, A068536, A102859, A113798, A202386, A256515.
%K A289140 nonn,base
%O A289140 1,1
%A A289140 _Giovanni Resta_, Jun 26 2017