A274567 - OEIS

%I #27 Aug 01 2020 01:16:43

%S 3,81,51,291,1251,339,62499,1971,5201,5001,175781251,7299

%N Least number k such that k^2-1 is the sum of two nonzero squares in exactly n ways.

%C a(11) > 25*10^5 if it exists. - _Chai Wah Wu_, Jul 23 2020

%C From _David A. Corneth_, Jul 23 2020: (Start)

%C a(13) <= 17578125001, a(17) <= 610351562499. (End)

%e a(2) = 81 because 81^2 - 1 = 28^2 + 76^2 = 44^2 + 68^2.

%Y Cf. A000404, A005563, A016032, A025426, A050795, A050797, A054994.

%K nonn,more

%O 1,1

%A _Altug Alkan_, Jun 28 2016

%E a(10) from _Chai Wah Wu_, Jul 22 2020