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A049735
Array T(i,j) is the number of lattice points (x,y) in circle with radius (0,0)-to-(i,j), read by antidiagonals.
10
1, 5, 5, 13, 9, 13, 29, 21, 21, 29, 49, 37, 25, 37, 49, 81, 57, 45, 45, 57, 81, 113, 89, 69, 61, 69, 89, 113, 149, 121, 97, 81, 81, 97, 121, 149, 197, 161, 129, 109, 101, 109, 129, 161, 197, 253, 213, 177, 145, 137, 137, 145, 177, 213, 253
OFFSET
0,2
COMMENTS
Specifically, x^2 + y^2 <= i^2 + j^2.
FORMULA
T(n,0) = A000328(n).
EXAMPLE
Antidiagonals (each starting on row 0):
{1},
{5, 5},
{13, 9, 13},
...
Array begins:
1 5 13 29 49 81
5 9 21 37 57 89
13 21 25 45 69 97
29 37 45 61 81 109
49 57 69 81 101 137
81 89 97 109 137 161
PROG
(PARI) T(n, k) = my(z=norml2([n, k]), m=ceil(sqrt(2)*max(n, k))); sum(x=-m, m, sum(y=-m, m, norml2([x, y]) <= z)); \\ Michel Marcus, Aug 07 2021
CROSSREFS
Cf. A000328 (1st column or row).
Sequence in context: A206553 A122213 A224067 * A055526 A146984 A055524
KEYWORD
nonn,tabl
STATUS
approved