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A079260
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Characteristic function of primes of form 4n+1 (1 if n is prime of form 4n+1, 0 otherwise).
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4
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0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Let M(n) denote the n X n matrix m(i,j)=0 if n divides ij-1, m(i,j) = 1 otherwise then det(M(n))=-1 if and only if n =2 or if n is prime ==1 (mod 4).
a(A002144(n)) = 1; a(A137409(n)) = 0. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 11 2008]
a(n) * A151763(n) = a(n).
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Index entries for characteristic functions
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PROG
| (PARI) { a(n)=if(n%4==1, isprime(n)) }; vector(100, n, a(n))
(Haskell)
a079260 n = fromEnum $ n `mod` 4 == 1 && a010051 n == 1
-- Reinhard Zumkeller, Oct 06 2011
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CROSSREFS
| Cf. A002144, A0792601.
Sequence in context: A011666 A011669 A023971 * A025457 A093957 A144601
Adjacent sequences: A079257 A079258 A079259 * A079261 A079262 A079263
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 04 2003
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