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%I #10 Oct 15 2013 22:31:27
%S 0,-1,0,1,0,-1,0,1,0,-1,0,1,-1,0,0,0,1,0,-1,0,0,0,1,-1,0,1,0,-1,0,1,
%T -1,0,0,0,1,-1,0,0,0,1,0,-1,0,0,0,1,-1,0,1,0,-1,0,0,0,1,-1,0,1,-1,0,0,
%U 0,1,-1,0,0,0,0,0,1,-1,0,1,0,-1,0,1,0,-1,0,1,-1,0,0,0,0,0,0,0,0,0,0,0,1,-1,0,1,-1,0,0,0,1,0,-1,0,0,0,0,0,0,0,1,0,-1,0
%N Second differences of A002808, the sequence of composites.
%H Reinhard Zumkeller, <a href="/A073445/b073445.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n)=c[n+2]-2c[n+1])+c[n], where c(n)=A002808(n).
%F a(n) = A073783(n+1) - A073783(n). - _Reinhard Zumkeller_, Jan 10 2013
%t c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[(c[w+2]-2*c[w+1])+c[w]), {w, 1, 1000}]
%o (Haskell)
%o a073445 n = a073445_list !! (n-1)
%o a073445_list = zipWith (-) (tail a073783_list) a073783_list
%o -- _Reinhard Zumkeller_, Jan 10 2013
%Y Also first differences of A054546.
%Y Cf. A002808, A054546.
%K sign
%O 1,1
%A _Labos Elemer_, Aug 01 2002
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