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 A105700 a(n)=1 if n is a prime, 2 if n is a semiprime, otherwise 0. 13
 0, 0, 1, 1, 2, 1, 2, 1, 0, 2, 2, 1, 0, 1, 2, 2, 0, 1, 0, 1, 0, 2, 2, 1, 0, 2, 2, 0, 0, 1, 0, 1, 0, 2, 2, 2, 0, 1, 2, 2, 0, 1, 0, 1, 0, 0, 2, 1, 0, 2, 0, 2, 0, 1, 0, 2, 0, 2, 2, 1, 0, 1, 2, 0, 0, 2, 0, 1, 0, 2, 0, 1, 0, 1, 2, 0, 0, 2, 0, 1, 0, 0, 2, 1, 0, 2, 2, 2, 0, 1, 0, 2, 0, 2, 2, 2, 0, 1, 0, 0, 0, 1, 0, 1, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS Antti Karttunen, Table of n, a(n) for n = 0..10000 FORMULA If A001222(n) <= 2, a(n) = A001222(n), otherwise a(n) = 0. - Antti Karttunen, Jul 26 2017 EXAMPLE a(4) = 1 because n=3 is a prime; a(5) = 2 because n=4 is a semiprime; a(9) = 0 because n=8 is not prime neither semiprime. MATHEMATICA psp[n_]:=Which[PrimeQ[n], 1, PrimeOmega[n]==2, 2, True, 0]; Join[{0}, Array[ psp, 110]] (* Harvey P. Dale, Sep 18 2011 *) PROG (Scheme) (define (A105700 n) (if (< (A001222 n) 3) (A001222 n) 0)) ;; Antti Karttunen, Jul 26 2017 CROSSREFS Cf. A001222, A105661. Sequence in context: A118829 A118832 A122807 * A236831 A030205 A159817 Adjacent sequences:  A105697 A105698 A105699 * A105701 A105702 A105703 KEYWORD easy,nonn AUTHOR Giovanni Teofilatto, May 04 2005 STATUS approved

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Last modified August 4 09:03 EDT 2020. Contains 336201 sequences. (Running on oeis4.)