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%I #19 Jun 27 2016 09:53:26
%S 2,221,2873,6409,97682,83317,8254129,237133,1416389,14080573,
%T 2789895602,3082729,41075281,82150562,239369741,9722453,403139914489,
%U 52406393,6733146600397009,520981201,40453486229,6941722489,13883444978,126391889,69177855149
%N Least number that is not divisible by 5 and the sum of two positive squares in exactly n ways.
%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%e a(2) = 221 because 221 = 5^2 + 14^2 = 10^2 + 11^2.
%t nR[n_] := (SquaresR[2, n] + Plus @@ Pick[{-4, 4}, IntegerQ /@ Sqrt[{n, n/2}]])/8; qn[w_] := Block[{z = Floor[(1/2) Times @@ (w + 1)]}, If[And @@ (EvenQ /@ w), z + {0, 1}, {z}]]; ric[w_, t_] := Block[{u = qn[w]}, If[ MemberQ[u, t], Sow@w];If[ Min[u] < t, ric[Append[w, 1], t]; u = w; u[[-1]]++; If[Length[u] == 1 || u[[-1]] <= u[[-2]], ric[u, t]]]]; val[w_] := {1, 2} Times @@ (Take[{13, 17, 29, 37, 41, 53}, Length@w]^w); a[1] =2; a[n_] := Min@ Select[ Flatten[ val /@ Reap[ric[{1}, n]][[2, 1]]], nR[#] == n &]; Array[a, 25] (* _Giovanni Resta_, Jun 27 2016 *)
%Y Cf. A016032, A047201.
%K nonn
%O 1,1
%A _Altug Alkan_, Jun 24 2016
%E a(7)-a(25) from _Giovanni Resta_, Jun 27 2016
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