A047808 a(n) counts different values of i^2 + j^2 <= n^2 or number of distances from the origin to all integer points inside a circle of radius n.

1, 2, 4, 7, 10, 14, 19, 24, 30, 37, 44, 52, 59, 69, 78, 87, 98, 109, 121, 133, 146, 158, 173, 186, 200, 216, 233, 249, 265, 283, 300, 318, 338, 357, 377, 398, 418, 439, 461, 482, 505, 528, 553, 576, 602, 626, 653, 680, 705, 735, 762, 790, 819, 847, 877, 904

Offset

0,2

Links

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

Formula

a(n) = number of b(i) <= n^2, b() = A001481.

Mathematica

Table[ Length@Union@Flatten@Table[ i^2+j^2, {i, 0, n}, {j, 0, Min[ i, Floor[ Sqrt[ n^2-i^2 ] ] ]} ], {n, 0, 64} ]

Crossrefs

Cf. A047809, A001481.

Sequence in context: A323623 A055607 A024512 * A007980 A022339 A025711

Adjacent sequences: A047805 A047806 A047807 * A047809 A047810 A047811

Keyword

nonn,easy,nice

Author

Wouter Meeussen, David W. Wilson

Status

approved