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%I #23 May 14 2020 17:46:54
%S 9,10,11,12,13,14,19,20,25,26,27,29,30,31,32,33,34,35,36,37,39,41
%N Number of n such that A247600(n) = 5.
%C Conjecture: This sequence has just 22 terms shown.
%C Sequence is finite and complete. Since pi(x) < 1.25506*x/log(x), it follows that for x > 106, pi(5*x) < x + 5. - _Chai Wah Wu_, May 01 2018, May 14 2020.
%F pi(5*a(n)) = a(n) + 5.
%e 9 is a term since pi(5*9) = 14 = 9 + 5, and pi(m*9) = 9 + m for no m < 5.
%Y Cf. A000720, A247600, A281197.
%K nonn,fini,full
%O 1,1
%A _Seiichi Manyama_, Jan 17 2017