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%I #15 Nov 26 2017 04:56:55
%S 3,3,4,4,4,4,5,5,5,5,5,5,6,6,5,5,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
%T 6,6,7,7,6,6,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
%U 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,8,8,8,8,8
%N Least k such that there are at least n primes between n and n*k.
%C a(9) = 5 is saying that there are 9 primes between 9 and 45, but actually there are 10: 11, 13, 17, 19, 23, 29, 31, 37, 41, 43. - _Michel Marcus_, Nov 20 2017
%e a(11) = 5 as there are 11 primes (13,17,19,23,29,31,37,41,43,47,53) between 11 and 55.
%o (PARI) a(n) = {k=2; while(sum(i=n+1, k*n-1, isprime(i)) < n, k++); k;} \\ _Michel Marcus_, Nov 22 2017
%K nonn
%O 1,1
%A _Amarnath Murthy_, Jan 03 2004
%E More terms from _John W. Layman_, Jan 20 2004
%E Name clarified by _Alois P. Heinz_, Nov 22 2017
%E Corrected by _Michel Marcus_, Nov 23 2017
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