A055428 Number of points in Z^n of norm <= 4.

1, 9, 49, 257, 1281, 5913, 23793, 88273, 306049, 995241, 3083569, 9217057, 26631041, 74164665, 198807793, 513829617, 1284656385, 3117323593, 7360510001, 16939394369, 38039783425, 83427144281, 178841051889

Offset

0,2

Links

Andrew Howroyd, Table of n, a(n) for n = 0..1000

Formula

Empirical g.f.: -(1201*x^16 +46896*x^15 +180864*x^14 -238504*x^13 -86788*x^12 +380032*x^11 -353440*x^10 +186568*x^9 -65418*x^8 +17264*x^7 -3968*x^6 +1000*x^5 -164*x^4 -32*x^3 +32*x^2 -8*x +1) / (x -1)^17. - Colin Barker, Jul 07 2013

Mathematica

a[n_] := SeriesCoefficient[1/(1-x) Sum[x^(i^2), {i, -4, 4}]^n, {x, 0, 16}];
a /@ Range[0, 22] (* Jean-François Alcover, Sep 29 2019, from A302997 *)

Crossrefs

Row n=4 of A302997.

Sequence in context: A181539 A224473 A146798 * A359186 A012231 A123270

Adjacent sequences: A055425 A055426 A055427 * A055429 A055430 A055431

Keyword

nonn

Author

David W. Wilson

Status

approved