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%I #9 Apr 10 2021 09:19:34
%S 1105,129,52,53,36,37,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,
%T 48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,
%U 71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89
%N a(n) is the smallest number that is the sum of n positive squares in four ways.
%C This is r(n,2,4) in Alter's notation.
%H R. Alter, <a href="https://doi.org/10.1007/BFb0096461">Computations and generalizations on a remark of Ramanujan</a>, pp. 182-196 of "Analytic Number Theory (Philadelphia, 1980)", ed. M. I. Knopp, Lect. Notes Math., Vol. 899, 1981. See Table 10, page 193.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F a(n) = n + 24 for n >= 8.
%e a(2) = 1105 = 4^2 + 33^2 = 9^2 + 32^2 = 12^2 + 31^2 = 23^2 + 24^2.
%e a(3) = 129 = 1^2 + 8^2 + 8^2 = 2^2 + 2^2 + 11^2 = 2^2 + 5^2 + 10^2 = 4^2 + 7^2 + 8^2.
%Y Cf. A343080, A343085, A343086.
%K nonn
%O 2,1
%A _Sean A. Irvine_, Apr 04 2021