This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A047077 Number of pairs of integers (x,y) with n^2 <= x^2+y^2 <= (n+1)^2. 3
 5, 12, 20, 24, 36, 44, 40, 52, 60, 68, 72, 68, 92, 96, 100, 100, 108, 120, 124, 132, 128, 148, 140, 144, 172, 180, 180, 168, 180, 204, 192, 212, 204, 220, 240, 212, 244, 232, 268, 260, 248, 276, 268, 292, 288, 276, 300, 296, 316, 324, 348, 336, 324, 348, 336 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Number of integer Cartesian grid points covered by a ring around the origin with width 1 and outer radius n. Also, number of Gaussian integers z=a+bi satisfying n-1 <= |z| <= n. - Ralf Stephan, Nov 28 2013 LINKS T. D. Noe, Table of n, a(n) for n = 0..1000 FORMULA a(n) = A000328(n+1) - A051132(n). MATHEMATICA a[n_] := Sum[SquaresR[2, k], {k, n^2, (n+1)^2}]; Table[a[n], {n, 0, 54}] (* Jean-François Alcover, Oct 15 2012 *) CROSSREFS Cf. A000328, A051132, A077770. Sequence in context: A017041 A139692 A099192 * A326663 A086570 A270333 Adjacent sequences:  A047074 A047075 A047076 * A047078 A047079 A047080 KEYWORD easy,nice,nonn AUTHOR Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Jan 26 2000 STATUS approved

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

Last modified October 16 02:52 EDT 2019. Contains 328038 sequences. (Running on oeis4.)