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A000205 Number of positive integers <= 2^n of form x^2 + 3 y^2.
(Formerly M2350 N0928)
0
1, 1, 3, 4, 8, 14, 25, 45, 82, 151, 282, 531, 1003, 1907, 3645, 6993, 13456, 25978, 50248, 97446, 189291, 368338, 717804, 1400699, 2736534, 5352182, 10478044, 20531668, 40264582, 79022464, 155196838, 304997408, 599752463, 1180027022, 2322950591, 4575114295 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

P. Moree and H. J. J. te Riele, The hexagonal versus the square lattice, Math. Comp. 73 (2004), no. 245, 451-473.

D. Shanks and L. P. Schmid, Variations on a theorem of Landau. Part I, Math. Comp., 20 (1966), 551-569.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=0..35.

P. Moree and H. J. J. te Riele, The hexagonal versus the square lattice

Index entries for sequences related to populations of quadratic forms

CROSSREFS

Cf. A000050.

Sequence in context: A023623 A023558 A170902 * A136425 A005907 A049866

Adjacent sequences:  A000202 A000203 A000204 * A000206 A000207 A000208

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified August 21 07:08 EDT 2017. Contains 290862 sequences.