A227453 Numbers k such that the distance to the largest square less than k is a multiple of 4.

8, 13, 20, 24, 29, 33, 40, 44, 48, 53, 57, 61, 68, 72, 76, 80, 85, 89, 93, 97, 104, 108, 112, 116, 120, 125, 129, 133, 137, 141, 148, 152, 156, 160, 164, 168, 173, 177, 181, 185, 189, 193, 200, 204, 208, 212, 216, 220, 224, 229, 233, 237, 241, 245, 249, 253, 260, 264, 268, 272, 276, 280

Offset: 1

Author

Ralf Stephan, Sep 22 2013

Keywords

• nonn

Comments

A071797(a(n)) = 4*m, A053186(a(n)+1) = 4*m, m > 0.

Apparently a bisection of A079896. While it may not be difficult to prove that the sequence is a subsequence of A079896, the apparent fact that a(n) = A079896(2n-1) is by no means obvious.

Examples

			8 - 2^2 = 1*4 and 24 - 4^2 = 2*4 so 8 and 24 are in the sequence.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A048760, A053186, A071797, A079896.

Programs

Mathematica

lsm4Q[n_]:=Module[{s=Floor[Sqrt[n]]^2},sHarvey P. Dale, Jun 20 2014 *)

PARI

is(n)=(n-sqrtint(n-1)^2)%4==0