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A105352
Numbers of points on successive rings of the simple square lattice.
1
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
1,2
COMMENTS
This is A004018 with the zero terms omitted.
a(n) = A004018(A001481(n)). - Franz Vrabec, Jun 14 2005
EXAMPLE
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).
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 *)
CROSSREFS
Cf. A004018, A001481; A057961 (partial sums).
Sequence in context: A010658 A128939 A342484 * A132200 A110757 A377468
KEYWORD
nice,nonn
AUTHOR
EXTENSIONS
Definition revised by N. J. A. Sloane, Oct 04 2013
STATUS
approved