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 A080545 Characteristic function of {1} union {odd primes}: 1 if n is 1 or an odd prime, else 0. 6
 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Antti Karttunen, Table of n, a(n) for n = 1..1001 FORMULA a(n) = (delta(Omega(n), 0) + delta(Omega(n), 1)) * d_0(n), where delta is the Kronecker delta function, Omega is the number of prime factors function (counted with multiplicity), and d_0(n) is the least significant digit of n in binary. - Alonso del Arte, Nov 19 2013 EXAMPLE a(2) = 0 because 2 is prime but even. a(3) = 1 because 3 is prime and odd. Likewise for a(5) and a(7). a(4) = 0 because 4 is neither prime nor odd. Likewise for a(6) and a(8). a(9) = 0 because 9 is odd but composite. MATHEMATICA Table[Boole[PrimeOmega[n] < 2 && OddQ[n]], {n, 100}] (* Alonso del Arte, Nov 19 2013 *) CROSSREFS Cf. A010051, A080355, A080339, A080567, A171387. Sequence in context: A286046 A189215 A285128 * A099991 A091069 A318608 Adjacent sequences:  A080542 A080543 A080544 * A080546 A080547 A080548 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Mar 21 2003 EXTENSIONS Added missing a(2) - Walter Roscello, Nov 19 2013 STATUS approved

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Last modified June 26 13:04 EDT 2022. Contains 354883 sequences. (Running on oeis4.)