A053457 Open disk numbers (version 2): a(n) is the number of points (i,j), i,j, integers, contained in an open disk of diameter n, centered at (0,1/2).

0, 0, 2, 6, 12, 16, 26, 38, 48, 60, 78, 94, 108, 128, 154, 174, 196, 224, 250, 278, 312, 344, 378, 410, 452, 484, 526, 574, 612, 652, 698, 754, 800, 848, 906, 958, 1012, 1068, 1130, 1190, 1252, 1316, 1378, 1446, 1516, 1588, 1654, 1730, 1808, 1880, 1954

Offset: 0

Author

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

Keywords

• easy
• nonn

Comments

a(n)/(n/2)^2->Pi

Crossrefs

Cf. A053414, A053456, A053458, A053459.