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Gilbreath transform of semiprimes (A001358).
1

%I #16 Sep 25 2023 18:55:54

%S 4,2,1,1,0,1,0,1,1,1,1,1,0,1,0,1,1,0,1,1,1,1,1,1,0,0,1,1,1,1,0,0,0,1,

%T 1,1,1,1,0,0,1,1,0,0,1,1,1,1,0,0,1,1,0,0,0,1,0,0,0,1,0,0,0,0,1,0,0,0,

%U 0,0,1,1,0,0,1,0,1,1,0,1,1,1,0,0,1,1,1

%N Gilbreath transform of semiprimes (A001358).

%H Paolo Xausa, <a href="/A365939/b365939.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Ge#Gilbreath">Index entries for sequences related to Gilbreath conjecture and transform</a>

%t A365939list[upto_]:=If[upto<4,{},Module[{d=Select[Range[upto],PrimeOmega[#]==2&]},Join[{4},Table[First[d=Abs[Differences[d]]],Length[d]-1]]]];A365939list[500] (* _Paolo Xausa_, Sep 25 2023 *)

%Y Leading terms of rows of the array in A131749.

%Y Cf. A001358, A196251, A361897, A362451.

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Sep 25 2023.

%E More terms from _Pontus von Brömssen_, Sep 25 2023