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%I #11 Feb 10 2019 23:03:07
%S 1,9,25,27,39,45,51,57,65,69,75,85,87,91,93,95,99,105,111,115,117,119,
%T 125,133,135,141,143,145,147,153,155,159,161,175,177,187,201,207,209,
%U 213,215,217,221,231,235,237,243,247,253,255,259,261,273,275,279,287
%N Odd nonprime numbers k such that composite(k) is even.
%p isA002808 := proc(n) n >= 4 and not isprime(n) ; end proc:
%p A002808 := proc(n) option remember ; local a; if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then return a; end if; end do; end if; end proc:
%p for n from 1 to 400 do if type(n,'odd') and not isprime(n) then c := A002808(n) ; if type(c,'even') then printf("%d,",n) ; end if; end if; end do: # _R. J. Mathar_, May 10 2010
%t With[{nn=400},Select[Flatten[Position[Complement[Range[4,nn], Prime[ Range[PrimePi[nn]]]],_?(EvenQ[#]&)]],OddQ[#]&&!PrimeQ[#]&]] (* _Harvey P. Dale_, Jun 23 2013 *)
%Y Cf. A002808, A141468.
%K nonn,less
%O 1,2
%A _Juri-Stepan Gerasimov_, Jan 20 2009
%E Edited by _N. J. A. Sloane_, Jan 30 2009
%E Corrected (67, 79, 113, 189, 219 removed) by _R. J. Mathar_, May 10 2010
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