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A051132 Number of ordered pairs of integers (x,y) with x^2+y^2 < n^2. 7
0, 1, 9, 25, 45, 69, 109, 145, 193, 249, 305, 373, 437, 517, 609, 697, 793, 889, 1005, 1125, 1245, 1369, 1513, 1649, 1789, 1941, 2109, 2285, 2449, 2617, 2809, 2997, 3205, 3405, 3613, 3841, 4049, 4281, 4509, 4765, 5013, 5249, 5521, 5785, 6073, 6349, 6621 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) = A000328(n) - A046109(n). [Reinhard Zumkeller, Jan 23 2012]

LINKS

T. D. Noe, Table of n, a(n) for n=0..1000

EXAMPLE

a(3)=25 from the points of shapes 00 (1), 10 (4), 11 (4), 20 (4), 21 (8), 22 (4).

MATHEMATICA

Table[Sum[SquaresR[2, k], {k, 0, n^2 - 1}], {n, 0, 46}]

PROG

(Haskell)

a051132 n = length [(x, y) | x <- [-n..n], y <- [-n..n], x^2 + y^2 < n^2]

-- Reinhard Zumkeller, Jan 23 2012

CROSSREFS

Changing "<" to "<=" in the definition gives A000328.

Sequence in context: A114057 A227518 A031036 * A247687 A075026 A113659

Adjacent sequences:  A051129 A051130 A051131 * A051133 A051134 A051135

KEYWORD

nonn,nice,easy

AUTHOR

Jostein Trondal (jostein.trondal(AT)protech.no)

EXTENSIONS

More terms from James A. Sellers

STATUS

approved

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Last modified December 20 23:03 EST 2014. Contains 252290 sequences.