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A213721 Smallest prime that is the sum of four nonzero squares in exactly n ways. 2

%I #15 Sep 04 2013 10:28:11

%S 2,7,31,67,97,103,157,199,277,223,307,383,439,367,547,463,673,613,577,

%T 751,643,733,787,727,853,983,997,967,1171,1223,1063,1087,1123,1613,

%U 1237,1279,1471,1453,1669,1423,1483,1597,1627,1543,1567,1747,2039,1753,1867,1951

%N Smallest prime that is the sum of four nonzero squares in exactly n ways.

%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>

%e a(2) = 31 because 31 = 2*1 + 4 + 25 = 4 + 3*9.

%t lst = {}; Do[p = 2; While[True, If[PrimeQ[p] && Length@Select[PowersRepresentations[p, 4, 2], ! MemberQ[#, 0] &] == n, AppendTo[lst, p]; Break[]]; p++], {n, 0, 49}]; lst

%Y Cf. A025416.

%K nonn

%O 0,1

%A _Arkadiusz Wesolowski_, Nov 02 2012

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Last modified April 19 16:21 EDT 2024. Contains 371794 sequences. (Running on oeis4.)