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Search: id:A004613
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| A004613 |
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Numbers that are divisible only by primes congruent to 1 mod 4. |
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+0
7
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| 1, 5, 13, 17, 25, 29, 37, 41, 53, 61, 65, 73, 85, 89, 97, 101, 109, 113, 125, 137, 145, 149, 157, 169, 173, 181, 185, 193, 197, 205, 221, 229, 233, 241, 257, 265, 269, 277, 281, 289, 293, 305, 313, 317, 325, 337, 349, 353, 365, 373, 377, 389, 397, 401, 409, 421
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Also gives solutions z to x^2+y^2=z^4 with GCD(x,y,z)=1 and x,y,z positive. - John Sillcox (johnsillcox(AT)hotmail.com), Feb 20 2004
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REFERENCES
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D. Cox, "Primes of Form x^2 + n y^2", Wiley, 1989.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
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FORMULA
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Numbers of the form x^2+y^2 where x is even, y is odd and gcd(x, y) = 1.
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PROGRAM
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(PARI) for(n=1, 1000, if(sumdiv(n, d, isprime(d)*if((d-1)%4, 1, 0))==0, print1(n, ", ")))
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CROSSREFS
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Essentially same as A008846.
Cf. A004614.
Sequence in context: A087445 A020882 A081804 this_sequence A008846 A120960 A094194
Adjacent sequences: A004610 A004611 A004612 this_sequence A004614 A004615 A004616
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KEYWORD
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nonn,nice,easy
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AUTHOR
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njas
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