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 A081309 Smallest prime p such that n-p is an 3-smooth number, a(n)=0 if no such prime exists. 2
 0, 0, 2, 2, 2, 2, 3, 2, 3, 2, 2, 3, 5, 2, 3, 7, 5, 2, 3, 2, 3, 13, 5, 23, 7, 2, 3, 19, 2, 3, 7, 5, 17, 2, 3, 0, 5, 2, 3, 13, 5, 41, 7, 17, 13, 19, 11, 47, 13, 2, 3, 43, 5, 53, 7, 2, 3, 31, 5, 59, 7, 53, 31, 37, 11, 2, 3, 41, 5, 43, 7, 71, 19, 2, 3, 67, 5, 0, 7, 53, 17, 73, 2, 3, 13, 5, 23, 7, 17, 89 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n)=0 iff A081308(n)=0. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 EXAMPLE a(25)=7: 25=7+2*3^2. PROG (Haskell) a081309 n | null ps   = 0           | otherwise = head ps           where ps = [p | p <- takeWhile (< n) a000040_list,                           a065333 (n - p) == 1] -- Reinhard Zumkeller, Jul 04 2012 CROSSREFS Cf. A081310, A081311, A081309, A000040, A003586. Cf. A065333. Sequence in context: A165035 A236531 A217403 * A010553 A262095 A163374 Adjacent sequences:  A081306 A081307 A081308 * A081310 A081311 A081312 KEYWORD nonn,look AUTHOR Reinhard Zumkeller, Mar 17 2003 STATUS approved

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Last modified May 27 06:24 EDT 2019. Contains 323599 sequences. (Running on oeis4.)