cp's OEIS Frontend

A332850 Numbers k = a^2 + b^2 such that reversal(k) = a^2 - b^2 for a > b > 0, where reversal is A004086.

%I A332850 #24 Apr 12 2025 03:43:52
%S A332850 699796,4854634,6752626,84036010,931910661,21584860960,52554850525,
%T A332850 467170024564,637843128736,638730439636,638734039636,638943127636,
%U A332850 727830438745,727834038745,746710459825,746754019825,748943127625,9894192267061,401309596403104,844181015028970
%N A332850 Numbers k = a^2 + b^2 such that reversal(k) = a^2 - b^2 for a > b > 0, where reversal is A004086.
%C A332850 When b=0, the palindromic numbers m = a^2 + b^2 such that reversal(m) = a^2 - b^2, are A002779 (palindromic squares).
%C A332850 a(19) > 3*10^14, if it exists. - _Giovanni Resta_, Feb 27 2020
%e A332850 699796 = 836^2 + 30^2 and 697996 = 836^2 - 30^2.
%t A332850 Do[If[IntegerReverse[a^2+b^2]==a^2-b^2,Print[{a^2+b^2,a,b}]],{a,1,50000},{b,1,a-1}]
%o A332850 (PARI) isok(k) = {my(r = fromdigits(Vecrev(digits(k))), s = r+k, d = k-r); d && !(s % 2) && issquare(s/2) && !(d % 2) && issquare(d/2); } \\ _Michel Marcus_, Feb 27 2020
%Y A332850 Cf. A002779, A004086, A035519, A055096, A202386.
%K A332850 nonn,base
%O A332850 1,1
%A A332850 _Metin Sariyar_, Feb 26 2020
%E A332850 a(6)-a(18) from _Giovanni Resta_, Feb 27 2020
%E A332850 a(19)-a(20) from _Jinyuan Wang_, Apr 10 2025