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%I #25 Oct 16 2023 12:04:55
%S 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,
%T 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,
%U 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
%N First differences of composite numbers.
%C Also, the highest common factors of pair of successive composite numbers. - _Amarnath Murthy_, Jan 31 2003
%C 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
%H Reinhard Zumkeller, <a href="/A073783/b073783.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A002808(n+1) - A002808(n).
%F a(n) = A073784(n) + 1.
%e a(7) = A002808(8) - A002808(7) = 15 - 14 = 1.
%t c[x_] := FixedPoint[x + PrimePi[#] + 1 &, x]; Differences[c /@ Range[106]] (* _Jayanta Basu_, Jul 09 2013 *)
%o (Haskell)
%o a073783 n = a073783_list !! (n-1)
%o a073783_list = zipWith (-) (tail a002808_list) a002808_list
%o -- _Reinhard Zumkeller_, Jan 10 2013
%o (PARI) m=4;forcomposite(n=6,1e3,print1(n-m", ");m=n) \\ _Charles R Greathouse IV_, Mar 20 2013
%Y Cf. A002808, A073784.
%Y a(n) = A136527(n, n+1).
%Y Cf. A073445 (first differences).
%K easy,nonn
%O 1,1
%A _Lior Manor_, Aug 11 2002
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