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A080339
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Characteristic function of {1} union {primes}: 1 if n is 1 or a prime, else 0.
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25
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1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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a(1)=1, and a(n) = Prod_{k=1...n-1}(k/n)^2 where (a/b) is the Jacobi symbol and n>1. - Dimitri Papadopoulos, Jan 13 2016
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MAPLE
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1, seq(`if`(isprime(i), 1, 0), i=2..100); # Robert Israel, Jan 11 2016
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MATHEMATICA
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Table[Which[n == 1, 1, PrimeQ[n], 1, True, 0], {n, 110}] (* Harvey P. Dale, Oct 03 2011 *)
Table[Boole[PrimeOmega[n] < 2], {n, 100}] (* Alonso del Arte, Nov 19 2013 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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