A274466 Least number that is not divisible by 5 and the sum of two positive squares in exactly n ways.

2, 221, 2873, 6409, 97682, 83317, 8254129, 237133, 1416389, 14080573, 2789895602, 3082729, 41075281, 82150562, 239369741, 9722453, 403139914489, 52406393, 6733146600397009, 520981201, 40453486229, 6941722489, 13883444978, 126391889, 69177855149

Offset

1,1

Links

Table of n, a(n) for n=1..25.

Index entries for sequences related to sums of squares

Example

a(2) = 221 because 221 = 5^2 + 14^2 = 10^2 + 11^2.

Mathematica

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 *)

Crossrefs

Cf. A016032, A047201.

Sequence in context: A124188 A261936 A332568 * A307511 A293945 A078276

Adjacent sequences: A274463 A274464 A274465 * A274467 A274468 A274469

Keyword

nonn

Author

Altug Alkan, Jun 24 2016

Extensions

a(7)-a(25) from Giovanni Resta, Jun 27 2016

Status

approved