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%I #7 May 08 2017 06:32:55
%S 19,23,33,35,47,59,63,71,75,77,95,103,107,118,124,129,131,143,147,155,
%T 161,167,179,187,195,201,203,206,209,215,217,223,236,239,243,247,248,
%U 251,271,275,280,283,285,287,294,299,311,316,323,327,329,332,334,339
%N Numbers that cannot be written as sum of two quarter-squares, cf. A002620.
%C A245575(a(n)) = 0.
%H Reinhard Zumkeller, <a href="/A245585/b245585.txt">Table of n, a(n) for n = 1..10000</a>
%t qsQ[n_] := qsQ[n] = With[{s = Sqrt[n]}, Which[IntegerQ[s], True, n == Floor[s] (Floor[s] + 1), True, True, False]];
%t A245575[n_] := Count[Range[0, n], k_ /; qsQ[k] && qsQ[n - k]];
%t Flatten[Position[Array[A245575, 1000, 0], 0]] - 1 (* _Jean-François Alcover_, May 08 2017 *)
%o (Haskell)
%o a245585 n = a245585_list !! (n-1)
%o a245585_list = filter ((== 0) . a245575) [0..]
%Y Cf. A002620, A245575.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Aug 04 2014
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