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%I #8 May 11 2019 17:00:51
%S 1,2,3,4,4,5,6,6,7,8,8,9,9,10,11,11,12,12,13,14,14,15,15,16,16,17,18,
%T 18,19,19,20,21,21,22,22,23,23,24,24,25,25,26,27,27,28,29,29,30,30,31,
%U 31,32,32,33,34,34,35,36,36,37,37,38,38,39,39,40,40,41,42,42,43,44,44,45
%N a(n) = PrimePi(A147819(n)).
%p A147819 := proc(n) if n = 1 then 2; else for a from procname(n-1)+1 do if isprime(a-1) or isprime(a+1) then if a <> 3 then return a; end if; end if; end do ; end if; end proc: A168389 := proc(n) numtheory[pi](A147819(n)) ; end proc: seq(A168389(n),n=1..100) ; # _R. J. Mathar_, Dec 03 2009
%Y Cf. A000720, A147819.
%K nonn
%O 1,2
%A _Giovanni Teofilatto_, Nov 24 2009
%E Extended beyond a(26) by _R. J. Mathar_, Dec 03 2009
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