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A106743
a(n) = -1 iff n is prime, a(n) = 1 iff n is not squarefree, otherwise (n is nonprime and squarefree) a(n) = 0.
1
0, -1, -1, 1, -1, 0, -1, 1, 1, 0, -1, 1, -1, 0, 0, 1, -1, 1, -1, 1, 0, 0, -1, 1, 1, 0, 1, 1, -1, 0, -1, 1, 0, 0, 0, 1, -1, 0, 0, 1, -1, 0, -1, 1, 1, 0, -1, 1, 1, 1, 0, 1, -1, 1, 0, 1, 0, 0, -1, 1, -1, 0, 1, 1, 0, 0, -1, 1, 0, 0, -1, 1, -1, 0, 1, 1, 0, 0, -1, 1, 1, 0, -1, 1, 0, 0, 0, 1, -1, 1, 0, 1, 0, 0, 0, 1, -1, 1, 1, 1, -1, 0, -1, 1, 0
OFFSET
1,1
LINKS
FORMULA
a(n) = 1 - 0^(A001222(n)-A001221(n)) - 0^(A001222(n)-1), for n>1. - Reinhard Zumkeller, May 23 2005
MATHEMATICA
Table[Which[PrimeQ[n], -1, SquareFreeQ[n], 0, True, 1], {n, 110}] (* Harvey P. Dale, Aug 30 2015 *)
PROG
(PARI) for(n=1, 105, print1(if(!issquarefree(n), 1, if(isprime(n), -1, 0)), ", "))
CROSSREFS
Cf. A000040 (prime), A013929 (not squarefree), A000469 (nonprime and squarefree), A082926.
Sequence in context: A069513 A092248 A354920 * A284944 A284674 A225181
KEYWORD
sign
AUTHOR
Giovanni Teofilatto, May 16 2005
EXTENSIONS
Edited and extended by Klaus Brockhaus, May 16 2005
STATUS
approved