A245585 Numbers that cannot be written as sum of two quarter-squares, cf. A002620.

19, 23, 33, 35, 47, 59, 63, 71, 75, 77, 95, 103, 107, 118, 124, 129, 131, 143, 147, 155, 161, 167, 179, 187, 195, 201, 203, 206, 209, 215, 217, 223, 236, 239, 243, 247, 248, 251, 271, 275, 280, 283, 285, 287, 294, 299, 311, 316, 323, 327, 329, 332, 334, 339

Offset: 1

Author

Reinhard Zumkeller, Aug 04 2014

Keywords

• nonn

Comments

A245575(a(n)) = 0.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002620, A245575.

Programs

Haskell

a245585 n = a245585_list !! (n-1)
a245585_list = filter ((== 0) . a245575) [0..]

Mathematica

qsQ[n_] := qsQ[n] = With[{s = Sqrt[n]}, Which[IntegerQ[s], True, n == Floor[s] (Floor[s] + 1), True, True, False]];
A245575[n_] := Count[Range[0, n], k_ /; qsQ[k] && qsQ[n - k]];
Flatten[Position[Array[A245575, 1000, 0], 0]] - 1 (* Jean-François Alcover, May 08 2017 *)