login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A053458 Open disk numbers (version 3): 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 (0,0). 4

%I

%S 0,1,1,7,13,19,31,43,55,73,85,109,121,151,169,199,235,253,295,313,361,

%T 397,433,475,511,571,595,661,703,757,817,859,925,979,1039,1111,1159,

%U 1237,1285,1381,1453,1519,1597,1663,1759,1813,1915,1993,2077,2173,2257

%N Open disk numbers (version 3): 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 (0,0).

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

%Y Cf. A053416, A053456, A053457, A053459.

%K easy,nonn

%O 0,4

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 16 07:30 EDT 2022. Contains 353693 sequences. (Running on oeis4.)