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Search: id:A002973
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| A002973 |
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a(n) is half of the even member of {x,y}, where x^2+y^2 is the n-th prime of the form 4i+1.
(Formerly M0135)
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+0
3
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| 1, 1, 2, 1, 3, 2, 1, 3, 4, 4, 2, 5, 5, 4, 2, 5, 3, 1, 5, 6, 7, 1, 4, 2, 8, 5, 7, 8, 1, 6, 7, 8, 9, 4, 9, 5, 3, 10, 10, 7, 6, 10, 2, 5, 11, 10, 5, 7, 10, 12, 4, 12, 9, 8, 2, 11, 3, 6, 13, 13, 11, 1, 13, 10, 6, 11, 13, 14, 7, 5, 9, 2, 3, 8, 10, 12, 5, 14, 2, 3, 14, 11, 15, 16, 16, 5, 15, 1, 8, 11
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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a(n) is odd iff x^2+y^2==5(mod 8). [From Vladimir Shevelev (shevelev(AT)bgu.ac.il), Jul 12 2009]
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
E. Kogbetliantz and A. Krikorian, Handbook of First Complex Prime Numbers, Gordon and Breach, NY, 1971, p. 243.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1000
S. R. Finch, Powers of Euler's q-Series, (arXiv:math.NT/0701251).
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EXAMPLE
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The 3rd prime of the form 4i+1 is 17=1^2+4^2, so a(3)=4/2=2.
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CROSSREFS
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Cf. A002144, A002972.
Sequence in context: A115624 A076291 A124458 this_sequence A071476 A071499 A039953
Adjacent sequences: A002970 A002971 A002972 this_sequence A002974 A002975 A002976
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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Better description from Jud McCranie (j.mccranie(AT)comcast.net), Mar 05 2003
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