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 A056608 Least prime factor of the n-th composite number. 36
 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 2, 2, 3, 2, 5, 2, 2, 3, 2, 2, 2, 3, 2, 2, 7, 2, 3, 2, 2, 5, 2, 3, 2, 2, 2, 3, 2, 5, 2, 2, 3, 2, 2, 2, 3, 2, 7, 2, 2, 3, 2, 2, 5, 2, 3, 2, 2, 7, 2, 3, 2, 5, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 7, 2, 11, 2, 3, 2, 5, 2, 2, 3, 2, 2, 7, 2, 3, 2, 2, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A020639(A002808(n)) = A000040(A118663(n)). - M. F. Hasler, Apr 03 2012 MATHEMATICA DeleteCases[Table[FactorInteger[n][[1, 1]] * Boole[Not[PrimeQ[n]]], {n, 2, 100}], 0] (* Alonso del Arte, Aug 21 2014 *) PROG (MAGMA) [ PrimeDivisors(n)[1]: n in [2..140] | not IsPrime(n) ]; // Klaus Brockhaus, Jun 23 2009 (Haskell) a056608 = a020639 . a002808  -- Reinhard Zumkeller, Mar 29 2014 (PARI) forcomposite(n=1, 1e2, p=factor(n)[1, 1]; print1(p, ", ")) \\ Felix FrÃ¶hlich, Aug 03 2014 (Python) from sympy import composite, factorint def A056608(n):     return min(factorint(composite(n))) # Chai Wah Wu, Jul 22 2019 CROSSREFS Cf. A052369 (largest prime factor of n, where n runs through composite numbers). [From Klaus Brockhaus, Jun 23 2009] Cf. A160180. Sequence in context: A306249 A064656 A270776 * A091787 A087040 A065569 Adjacent sequences:  A056605 A056606 A056607 * A056609 A056610 A056611 KEYWORD easy,nonn AUTHOR Odimar Fabeny, Aug 07 2000 EXTENSIONS More terms from James A. Sellers, Aug 25 2000 Definition corrected by Reinhard Zumkeller, Mar 29 2014 Name changed by Alonso del Arte, Aug 21 2014 STATUS approved

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Last modified January 29 08:12 EST 2020. Contains 331337 sequences. (Running on oeis4.)