0,2

Number of points of L_infinity norm n in the simple square lattice Z^2. - N. J. A. Sloane (njas(AT)research.att.com), Apr 15 2008

Apart from initial term(s), dimension of the space of weight 2n cusp forms for Gamma_0( 24 ).

Number of 4 X n binary matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1), (01;0), (11;0) and (01;1). An occurrence of a ranpp (xy;z) in a matrix A=(a(i,j)) is a triple (a(i1,j1), a(i1,j2), a(i2,j1)) where i1<i2, j1<j2 and these elements are in same relative order as those in the triple (x,y,z). - Sergey Kitaev (kitaev(AT)ms.uky.edu), Nov 11 2004

These numbers correspond to the number of primes in the shells of a prime spiral. In a(2) there are 8 primes surrounding 2 in a prime spiral - Enoch Haga (Enokh(AT)comcast.net), Apr 06 2000.

R. Bacher, P. de la Harpe and B. Venkov, Series de croissance et series d'Ehrhart associees aux reseaux de racines, C. R. Acad. Sci. Paris, 325 (Series 1) (1997), 1137-1142.

J. Serra-Sagrista, Enumeration of lattice points in l_1 norm, Information Processing Letters, 76, no. 1-2 (2000), 39-44.

S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, Integers: Electronic Journal of Combinatorial Number Theory 4 (2004), A21, 20pp.

S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, University of Kentucky Research Reports (2004).

William A. Stein, Dimensions of the spaces S_k(Gamma_0(N))

William A. Stein, The modular forms database

((1+x)/(1-x))^2 if norm is even; otherwise 0.

G.f. for coordination sequence of B_n lattice: Sum(binomial(2*n+1, 2*i)*z^i, i=0..n)-2*n*z*(1+z)^(n-1))/(1-z)^n. [Bacher et al.]

a(n) = (2n+1)^2 - (2n-1)^2. Binomial transform of [1, 7, 1, -1, 1, -1, 1,...] - Gary W. Adamson (qntmpkt(AT)yahoo.com), Dec 27 2007

a=1; lst={a}; Do[b=n^2-a; AppendTo[lst, b]; a+=b, {n, 3, 6!, 2}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), May 18 2009]

Essentially the same as A008590.

Sequence in context: A044848 A044893 A008590 this_sequence A061824 A085131 A043421

Adjacent sequences: A022141 A022142 A022143 this_sequence A022145 A022146 A022147

nonn

mbaake(AT)sunelc3.tphys.physik.uni-tuebingen.de (Michael Baake)