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 A092573 Number of solutions to x^2 + 3y^2 = n in positive integers x and y. 11
 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 3, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 3, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 3, 0, 0, 1, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 2, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,29 LINKS Robert Israel, Table of n, a(n) for n = 0..10000 E. Akhtarkavan, M. F. M. Salleh and O. Sidek, Multiple Descriptions Video Coding Using Coinciding Lattice Vector Quantizer for H.264/AVC and Motion JPEG2000, World Applied Sciences Journal 21 (2): 157-169, 2013. - From N. J. A. Sloane, Feb 11 2013 Mohammad K. Azarian, Diophantine Pair, Problem B-881, Fibonacci Quarterly, Vol. 37, No. 3, August 1999, pp. 277-278; Solution to Problem B-881, Fibonacci Quarterly, Vol. 38, No. 2, May 2000, pp. 183-184. Eric Weisstein's World of Mathematics, Euler's 6n+1 Theorem FORMULA a(n) = ( A033716(n) - A000122(n) - A000122(n/3) + A000007(n) )/4. - Max Alekseyev, Sep 29 2012 G.f.: (Theta_3(0,x)-1)*(Theta_3(0,x^3)-1)/4 where Theta_3 is a Jacobi theta function. - Robert Israel, Apr 03 2017 MAPLE N:= 300: # to get a(0)..a(N) V:= Vector(N): for y from 1 to floor(sqrt(N/3-1)) do   js:= [seq(x^2+3*y^2, x=1..floor(sqrt(N-3*y^2)))];   V[js]:= map(`+`, V[js], 1); od: 0, op(convert(V, list)); # Robert Israel, Apr 03 2017 MATHEMATICA r[z_] := Reduce[x > 0 && y > 0 && x^2 + 3 y^2 == z, {x, y}, Integers]; Table[rz = r[z]; If[rz === False, 0, If[rz[[0]] === Or, Length[rz], 1]], {z, 0, 102}] (* Jean-François Alcover, Oct 23 2012 *) gf = (EllipticTheta[3, 0, x]-1)*(EllipticTheta[3, 0, x^3]-1)/4 + O[x]^105; CoefficientList[gf, x] (* Jean-François Alcover, Jul 02 2018, after Robert Israel *) CROSSREFS Cf. A002476, A092572, A092575. Sequence in context: A109898 A223074 A192732 * A307801 A186717 A233286 Adjacent sequences:  A092570 A092571 A092572 * A092574 A092575 A092576 KEYWORD nonn AUTHOR Eric W. Weisstein, Feb 28 2004 EXTENSIONS Definition corrected by David A. Corneth, Apr 03 2017 STATUS approved

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Last modified May 7 15:02 EDT 2021. Contains 343650 sequences. (Running on oeis4.)