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a(n) = largest number k that is not the sum of {2 squares, a nonnegative 5th power, and a nonnegative n-th power}.
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%I #11 Mar 20 2020 20:03:52

%S 71,2543,146687,55871,63703,353087,606239,21073228,4606428,19212172,

%T 16301375,88507864,228238087,126691212,121909855,366845415,448525727,

%U 1818767247,1319413228,341968924,673747279,188739607,2366756975,1770393855,411629407,1240489516

%N a(n) = largest number k that is not the sum of {2 squares, a nonnegative 5th power, and a nonnegative n-th power}.

%C All terms are conjectural and have only been checked up to 4*10^9.

%H W. Jagy and I. Kaplansky, <a href="https://projecteuclid.org/euclid.em/1062621075">Sums of Squares, Cubes and Higher Powers</a>, Experimental Mathematics, vol. 4 (1995) pp. 169-173.

%e a(4) = 2543, since 2543 is the greatest number such that is not the sum of {2 squares, a nonnegative 5th power, and a 4th power} (at least up to 4*10^9).

%Y Cf. A022566, A111151, A299796.

%K nonn

%O 3,1

%A _XU Pingya_, Feb 19 2020