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A131377
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Starting with 1, the sequence a(n) changes from 1 to 0 or back when the next number n is a prime.
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2
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1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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FORMULA
| a(n) = 1 - A071986(n).
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EXAMPLE
| n = 0, 1, 2, 3, 4, 5, etc..
a(n)= 1, 1, 0, 1, 1, 0, etc.
Starting with 1 the sequence changes when we move from 1 to 2 because 2 is prime, again from 2 to 3 because also 3 is prime, then from 4 to 5 being 5 prime and so on.
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MAPLE
| P:=proc(n) local i, k; k:=1; for i from 0 by 1 to n do if isprime(i) then if k=1 then k:=0; else k:=1; fi; fi; print(k); od; end: P(100);
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CROSSREFS
| Cf. A131378.
Cf. A071986 - Omar E. Pol, Feb 19 2011.
Sequence in context: A175480 A014577 A157926 * A077049 A124895 A089885
Adjacent sequences: A131374 A131375 A131376 * A131378 A131379 A131380
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KEYWORD
| easy,nonn
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AUTHOR
| Paolo P. Lava & Giorgio Balzarotti (paoloplava(AT)gmail.com), Jul 04 2007
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