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 A162022 Smallest prime factor of n-th odd composite integers A071904. 4
 3, 3, 3, 5, 3, 3, 5, 3, 3, 7, 3, 5, 3, 3, 5, 3, 3, 7, 3, 5, 3, 7, 3, 5, 3, 3, 3, 5, 3, 7, 11, 3, 5, 3, 7, 3, 3, 11, 5, 3, 3, 5, 3, 7, 3, 13, 3, 5, 3, 3, 5, 11, 3, 3, 3, 7, 5, 3, 11, 3, 5, 7, 3, 13, 3, 3, 5, 3, 3, 5, 13, 3, 11, 3, 7, 3, 5, 3, 3, 5, 3, 3, 7, 17, 3, 5, 3, 13, 7, 3, 5, 3, 3, 11, 3, 17, 5, 3, 7, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Records are for n's such that A071904(n) = squares of primes. a(n) = A020639(A071904(n)). [Reinhard Zumkeller, Oct 10 2011] LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 EXAMPLE A071904(1)=9, hence a(1)=3, A071904(4)=25, hence a(4)=5. MATHEMATICA nn=501; With[{ci=Complement[Range[9, nn, 2], Prime[Range[PrimePi[nn]]]]}, FactorInteger[ #][[1, 1]]&/@ci] (* Harvey P. Dale, Nov 30 2012 *) PROG (Python) from sympy import primepi, primefactors def A162022(n): if n == 1: return 3 m, k = n, primepi(n) + n + (n>>1) while m != k: m, k = k, primepi(k) + n + (k>>1) return min(primefactors(m)) # Chai Wah Wu, Jul 31 2024 CROSSREFS Cf. A014076, A071904. Sequence in context: A002373 A236569 A103153 * A318240 A262289 A096918 Adjacent sequences: A162019 A162020 A162021 * A162023 A162024 A162025 KEYWORD nonn,changed AUTHOR Zak Seidov, Jun 25 2009 EXTENSIONS Corrected example a(4)=5 Francesco Antoni (francesco_antoni(AT)yahoo.com), Aug 04 2010 STATUS approved

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Last modified August 7 20:39 EDT 2024. Contains 375017 sequences. (Running on oeis4.)