id:A105661 - OEIS Search Results

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a(n)=1 if n is a prime, 2 if n is an even semiprime, otherwise 0.

+0
2

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; listen)

	OFFSET	`1,4`
	EXAMPLE	`a(3)=1 because n=3 is a prime;` `a(4)=2 because n=4=22 is an even semiprime;` `a(8)=0 because n=8 is neither prime nor semiprime.` `a(15)=0 because n=15=35 is an odd semiprime.`
	PROGRAM	`(PARI) for(n=1, 105, if((n%2==0)&&(bigomega(n)==2), r=2, r=isprime(n)); print1(r, ", "))`
	CROSSREFS	`Cf. A001222.` `Sequence in context: A143947 A073781 A048622 this_sequence A082451 A121362 A091704` `Adjacent sequences: A105658 A105659 A105660 this_sequence A105662 A105663 A105664`
	KEYWORD	`easy,nonn`
	AUTHOR	`Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), May 04 2005`
	EXTENSIONS	`Corrected and extended by Rick L. Shepherd (rshepherd2(AT)hotmail.com), May 17 2005`

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Last modified December 5 23:38 EST 2009. Contains 170428 sequences.

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