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 A073783 First differences of composite numbers. 9
 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 2, 2, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also, the highest common factors of pair of successive composite numbers. - Amarnath Murthy, Jan 31 2003 A073783(n) = A073784(n) + 1. All terms are 1 or 2. Runs of 1's may be of arbitrary lengths, while the lengths of runs of 2's are 1 or 2.  - Zak Seidov, Mar 18 2013 LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A002808(n+1) - A002808(n). EXAMPLE a(7) = A002808(8) - A002808(7) = 15 - 14 = 1. MATHEMATICA c[x_] := FixedPoint[x + PrimePi[#] + 1 &, x]; Differences[c /@ Range[106]] (* Jayanta Basu, Jul 09 2013 *) PROG (Haskell) a073783 n = a073783_list !! (n-1) a073783_list = zipWith (-) (tail a002808_list) a002808_list -- Reinhard Zumkeller, Jan 10 2013 (PARI) m=4; forcomposite(n=6, 1e3, print1(n-m", "); m=n) \\ Charles R Greathouse IV, Mar 20 2013 CROSSREFS Cf. A002808, A073784. a(n) = A136527(n, n+1). Cf. A073445 (first differences). Sequence in context: A026605 A270646 A293540 * A134430 A130658 A014695 Adjacent sequences:  A073780 A073781 A073782 * A073784 A073785 A073786 KEYWORD easy,nonn AUTHOR Lior Manor Aug 11 2002 STATUS approved

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Last modified December 17 06:45 EST 2018. Contains 318192 sequences. (Running on oeis4.)