Voozh

A088897

T(n,k) = number of ordered pairs of integers (x,y) with x^2/n^2 + y^2/k^2 <= 1, 1<=k<=n; triangular array, read by rows.

5, 7, 13, 9, 19, 29, 11, 25, 35, 49, 13, 31, 45, 63, 81, 15, 37, 55, 73, 91, 113, 17, 43, 65, 87, 109, 131, 149, 19, 45, 71, 97, 123, 145, 175, 197, 21, 51, 81, 107, 141, 163, 197, 223, 253, 23, 57, 91, 121, 159, 185, 219, 245, 279, 317, 25, 63, 101, 135, 169

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OFFSET

1,1

COMMENTS

T(n,k) = number of lattice points covered by an ellipse with semimajor axis = n, semiminor axis = k and center = (0,0).

a(n) = A088898(n) + A088899(n);

T(n,n) = A000328(n).

LINKS

Table of n, a(n) for n=1..60.

Eric Weisstein's World of Mathematics, Ellipse

MATHEMATICA

T[n_, k_] := Reduce[x^2/n^2 + y^2/k^2 <= 1, {x, y}, Integers] // Length;