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A173229 a(n) is the n-th number m such that 6m-1 is composite minus the n-th number k such that 6k+1 is composite.

%I A173229 #8 Feb 07 2019 02:13:01
%S A173229 2,3,4,2,5,2,4,4,3,3,5,4,2,1,2,5,6,7,7,6,6,6,4,7,5,4,6,4,4,4,4,5,5,6,
%T A173229 5,7,8,7,6,6,6,8,8,9,9,10,8,8,12,8,9,8,9,8,8,8,7,8,7,8,6,4,3,4,4,6,7,
%U A173229 6,6,6,8,6,6,5,5,6,8,7,10,9,9,9,11,11,11,12,11,10,9,7,10,8,8,6,6,6,4,5,5,7
%N A173229 a(n) is the n-th number m such that 6m-1 is composite minus the n-th number k such that 6k+1 is composite.
%C A173229 A046953 U A046954(without zero) = A067611 where A067611 U A002822 U A171696 = A001477.
%F A173229 a(n) = A046953(n) - A046954(n+1).
%e A173229 a(1) = 6 - 4 = 2;
%e A173229 a(2) = 11 - 8 = 3;
%e A173229 a(3) = 13 - 9 = 4.
%p A173229 A046953 := proc(n) if n = 1 then 6 ; else for a from procname(n-1)+1 do if not isprime(6*a-1) then return a; end if; end do: end if; end proc:
%p A173229 A046954 := proc(n) if n = 1 then 0 ; else for a from procname(n-1)+1 do if not isprime(6*a+1) then return a; end if; end do: end if; end proc:
%p A173229 A173229 := proc(n) A046953(n)-A046954(n+1) ; end proc:
%p A173229 seq(A173229(n),n=1..120) ; # _R. J. Mathar_, May 02 2010
%Y A173229 Cf. A001477, A002822, A067611, A046953, A046954, A171696.
%K A173229 nonn
%O A173229 1,1
%A A173229 _Juri-Stepan Gerasimov_, Feb 13 2010, Feb 14 2010
%E A173229 Corrected from a(63) onwards by _R. J. Mathar_, May 02 2010