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A169783 Number of solutions to a^2 + b^2 + 4*c^2 = n. 3
1, 4, 4, 0, 6, 16, 8, 0, 12, 20, 8, 0, 8, 16, 16, 0, 6, 32, 12, 0, 24, 32, 8, 0, 24, 20, 24, 0, 0, 48, 16, 0, 12, 32, 16, 0, 30, 16, 24, 0, 24, 64, 16, 0, 24, 48, 16, 0, 8, 36, 28, 0, 24, 48, 32, 0, 48, 32, 8, 0, 0, 48, 32, 0, 6, 64, 32, 0, 48, 64, 16, 0, 36, 32, 40, 0, 24, 64, 16, 0, 24, 68 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
G.f.: theta_3(q)^2*theta_3(q^4), where theta_3() is the Jacobi theta function. - Ilya Gutkovskiy, Aug 01 2018
MAPLE
t0:=Array(0..10000, 0); M:=15;
for i from -M to M do for j from -M to M do for k from -M to M do
t1:=i^2+j^2+4*k^2; t0[t1]:=t0[t1]+1; od: od: od:
[seq(t0[i], i=0..100)];
CROSSREFS
x^2+y^2+k*z^2: A005875, A014455, A034933, A169784.
Sequence in context: A228048 A016705 A245592 * A133657 A121455 A227033
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 12 2010
STATUS
approved

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Last modified March 29 06:15 EDT 2024. Contains 371265 sequences. (Running on oeis4.)