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
Links
- T. D. Noe, Table of n, a(n) for n = 0..1000
Programs
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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} ]
Formula
a(n) = number of b(i) <= n^2, b() = A001481.