|
Search: id:A000074
|
|
|
| A000074 |
|
Number of odd integers <= 2^n of form x^2 + y^2.
(Formerly M1077 N0407)
|
|
+0
1
|
|
| 1, 1, 2, 4, 7, 13, 25, 43, 83, 157, 296, 564, 1083, 2077, 4006, 7733, 14968, 29044, 56447, 109864, 214197, 418080, 816907, 1598040, 3129063, 6132106
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
REFERENCES
|
D. Shanks, The second-order term in the asymptotic expansion of B(x), Math. Comp., 18 (1964), 75-86.
|
|
LINKS
|
Index entries for sequences related to populations of quadratic forms
|
|
EXAMPLE
|
a(4)=4 since 2^4=16 and 1=1^2, 5=1^2+2^2, 9=3^2, 13=2^2+3^2.
|
|
PROGRAM
|
(PARI) a(n)=if(n<0, 0, sum(k=1, 2^(n-1), 0<sum(y=0, sqrtint(2*k-1), issquare(2*k-1-y^2))))
|
|
CROSSREFS
|
Adjacent sequences: A000071 A000072 A000073 this_sequence A000075 A000076 A000077
Sequence in context: A102112 A102113 A034440 this_sequence A079958 A018082 A018083
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
njas
|
|
|
Search completed in 0.002 seconds
|
