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A105661
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a(n)=1 if n is a prime, 2 if n is an even semiprime, otherwise 0.
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0, 1, 1, 2, 1, 2, 1, 0, 0, 2, 1, 0, 1, 2, 0, 0, 1, 0, 1, 0, 0, 2, 1, 0, 0, 2, 0, 0, 1, 0, 1, 0, 0, 2, 0, 0, 1, 2, 0, 0, 1, 0, 1, 0, 0, 2, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 2, 1, 0, 1, 2, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 2, 0, 0, 0, 0, 1, 0, 0, 2, 1, 0, 0, 2, 0, 0, 1, 0, 0, 0, 0, 2, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,4
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EXAMPLE
| a(3)=1 because n=3 is a prime;
a(4)=2 because n=4=2*2 is an even semiprime;
a(8)=0 because n=8 is neither prime nor semiprime.
a(15)=0 because n=15=3*5 is an odd semiprime.
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PROG
| (PARI) for(n=1, 105, if((n%2==0)&&(bigomega(n)==2), r=2, r=isprime(n)); print1(r, ", "))
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CROSSREFS
| Cf. A001222.
Sequence in context: A143947 A073781 A048622 * A082451 A121362 A091704
Adjacent sequences: A105658 A105659 A105660 * A105662 A105663 A105664
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KEYWORD
| easy,nonn
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AUTHOR
| Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), May 04 2005
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EXTENSIONS
| Corrected and extended by Rick L. Shepherd (rshepherd2(AT)hotmail.com), May 17 2005
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