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Search: id:A101264
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| A101264 |
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a(n) = 1 iff 2*n+1 is prime, else a(n) = 0. |
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+0
9
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| 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Taking the inverse Moebius transform produces an interesting sequence! - Jonathan Vos Post, Dec 19 2004
Inverse Mobius transform of the sequence, after dropping a(0), yields A086668. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 25 2009]
If we drop a(0) then we may describe the sequence as: for all numbers k(n) [k(n) = 4 ceil(n/2) + (-1)^n] congruent to -1 or +1 (mod 4) starting with k(n) = {3,5,7,9,11,...}, a(k(n)) is 1 if k(n) is prime and 0 if k(n) is composite. [From Daniel Forgues (squid(AT)zensearch.com), Mar 01 2009]
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LINKS
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Daniel Forgues, Table of n, a(n) for n=0,...,49999
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FORMULA
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a(n) = A057427(A085090(n+1)). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Sep 14 2006
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EXAMPLE
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a(1) = 1 because 2*1+1 = 3 is prime;
a(2) = 1 because 2*2+1 = 5 is prime;
a(3) = 1 because 2*3+1 = 7 is prime;
a(4) = 0 because 2*4+1 = 9 is composite;
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MATHEMATICA
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Table[If[PrimeQ[2n + 1], 1, 0], {n, 0, 104}] (Ray Chandler)
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CROSSREFS
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Bisection (odd n) of A010051.
Cf. A065091, A063524.
If we drop a(0), equals absolute value of A156707. [From Daniel Forgues (squid(AT)zensearch.com), Mar 01 2009]
Sequence in context: A130854 A165191 A112448 this_sequence A095770 A140318 A060584
Adjacent sequences: A101261 A101262 A101263 this_sequence A101265 A101266 A101267
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KEYWORD
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easy,nonn
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AUTHOR
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Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Dec 18 2004
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EXTENSIONS
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Corrected by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 09 2005
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