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 A055428 Number of points in Z^n of norm <= 4. 2
 1, 9, 49, 257, 1281, 5913, 23793, 88273, 306049, 995241, 3083569, 9217057, 26631041, 74164665, 198807793, 513829617, 1284656385, 3117323593, 7360510001, 16939394369, 38039783425, 83427144281, 178841051889 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified April 13 21:58 EDT 2024. Contains 371645 sequences. (Running on oeis4.)