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A073092
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Number of numbers of the form x^2+y^2 (0 <= x <= y) less than or equal to n.
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0
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1, 2, 3, 3, 4, 5, 5, 5, 6, 7, 8, 8, 8, 9, 9, 9, 10, 11, 12, 12, 13, 13, 13, 13, 13, 15, 16, 16, 16, 17, 17, 17, 18, 18, 19, 19, 20, 21, 21, 21, 22, 23, 23, 23, 23, 24, 24, 24, 24, 25, 27, 27, 28, 29, 29, 29, 29, 29, 30, 30, 30, 31, 31, 31, 32, 34, 34, 34, 35, 35, 35, 35, 36, 37, 38
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n)=sum(k=0, n, A000161(k)); a(n) is asymptotic to Pi*n/8.
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EXAMPLE
| 0^2+0^2, 0^2+1^2, 1^2+1^2 are less than or equal to 2 hence a(2)=3.
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PROG
| (PARI) a(n)=sum(x=0, n, sum(y=0, x, if((sign(x^2+y^2-n)+1)*sign(x^2+y^2-n), 0, 1)))
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CROSSREFS
| Cf. A000161, A001481.
Cf. A057655.
Sequence in context: A202305 A195778 A165706 * A088023 A061451 A205542
Adjacent sequences: A073089 A073090 A073091 * A073093 A073094 A073095
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KEYWORD
| easy,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 18 2002
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