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A053459 Open disk numbers (version 4): a(n) is the number of points (i+j/2,j*sqrt(3)/2), i,j integers (triangular grid) contained in an open disk of diameter n, centered at (1/2,0). 3
0, 0, 4, 8, 14, 22, 30, 42, 60, 74, 92, 108, 130, 148, 178, 206, 230, 262, 288, 324, 364, 400, 442, 480, 522, 562, 614, 662, 712, 764, 812, 868, 922, 988, 1050, 1106, 1176, 1234, 1312, 1376, 1452, 1528, 1598, 1678, 1750, 1838, 1920, 2006, 2092, 2172, 2266 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n)/(n/2)^2 -> Pi*2/sqrt(3).

LINKS

Table of n, a(n) for n=0..50.

CROSSREFS

Cf. A053417, A053456, A053457, A053458.

Sequence in context: A312707 A337232 A004797 * A024398 A054347 A194149

Adjacent sequences:  A053456 A053457 A053458 * A053460 A053461 A053462

KEYWORD

easy,nonn

AUTHOR

Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jan 13 2000

STATUS

approved

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Last modified May 17 14:19 EDT 2022. Contains 353746 sequences. (Running on oeis4.)