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%I #9 Dec 29 2023 10:31:46
%S 9,21,25,27,33,63,77,81,93,105,125,143,147,153,165,171,175,185,235,
%T 243,247,249,255,273,285,301,321,335,345,363,405,437,473,475,483,517,
%U 529,533,559,567,579,585,591,603,627,671,689,711,767,789,793,825,861,873,891,897
%N Odd composites of the form n-(p(n+2)-p(n))/(p(n+1)-p(n-1)), where p(n)=n-th prime.
%C Entries are not repeated and shown in natural order.
%H Harvey P. Dale, <a href="/A141603/b141603.txt">Table of n, a(n) for n = 1..1000</a>
%e n=10: 10-(37-29)/(31-23)=9=a(1).
%e n=22: 22-(89-79)/(83-73)=21=a(2).
%e n=26: 26-(107-101)/(103-97)=25=a(3).
%e n=28: 28-(113-107)/(109-103)=27=a(4).
%e n=34: 34-(151-139)/(149-137)=33=a(5).
%t f[{a_,b_,c_,d_}]:=(d-b)/(c-a); Select[Table[n-f[Prime[Range[n-1,n+2]]],{n,2,1000}],OddQ[#]&&CompositeQ[#]&]//Union (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Dec 15 2018 *)
%Y Cf. A000040.
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, Sep 10 2008
%E Corrected and extended by _R. J. Mathar_, Sep 26 2008
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