A105352 Numbers of points on successive rings of the simple square lattice.

1, 4, 4, 4, 8, 4, 4, 8, 8, 4, 8, 4, 8, 12, 8, 8, 4, 8, 4, 8, 8, 8, 8, 4, 12, 8, 8, 8, 8, 4, 16, 8, 4, 8, 8, 8, 4, 8, 16, 8, 8, 8, 4, 12, 8, 8, 8, 8, 8, 8, 8, 4, 8, 16, 4, 16, 8, 8, 4, 16, 8, 8, 8, 8, 8, 8, 4, 8, 12, 16, 8, 8, 8, 8, 16, 8, 8, 4, 8, 12, 8, 16, 8, 8, 8, 16, 12, 8, 8, 8, 8, 8, 8, 4, 8, 8, 16, 4

Offset: 1

Author

Sébastien Dumortier, Apr 30 2005

Keywords

• nice
• nonn

Comments

This is A004018 with the zero terms omitted.

a(n) = A004018(A001481(n)). - Franz Vrabec, Jun 14 2005

Examples

			a(1) = 1 from (0, 0).
a(2) = 4 from (0, 1), (0, -1), (1, 0), (-1, 0).
a(5) = 8 from (+-1, +-2), (+-2, +-1).
		

Links

• T. D. Noe, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A004018, A001481; A057961 (partial sums).

Programs

Mathematica

max = 100; A001481 = Select[Range[0, 4*max], SquaresR[2, #] != 0 &]; A004018[n_] := SquaresR[2, n]; a[n_] := A004018[A001481[[n]]]; Table[a[n], {n, 1, max}] (* Jean-François Alcover, Oct 04 2013, after Franz Vrabec *)

Extensions

Definition revised by N. J. A. Sloane, Oct 04 2013