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Numbers n such that PrimePi(prime(n + 1)^2) - PrimePi(prime(n)^2) < c*n with c=9/5.
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%I #2 Mar 30 2012 17:31:17

%S 7,10,13,20,26,28,33,35,43,45,49,52,57,60,64,89,98,109,113,116,120,

%T 140,142,144,148,152,171,173,176,178,182,190,201,209,212,215,225,230,

%U 234,236,253,256,262,265,268,277,286,288,294,296,302,307,313,315,318,320

%N Numbers n such that PrimePi(prime(n + 1)^2) - PrimePi(prime(n)^2) < c*n with c=9/5.

%C If c=2 instead of 1.8 then the sequence is A029707.

%C This sequence is probably finite with 699 terms with 14020 being the last.

%C If c=1.7 the sequence is just {7, 10, 13, 20, 26, 28, 33, 35, 45, 49, 57, 60, 64, 89, 98, 109, 113, 116, 171, 190, 201, 215, 225, 234, 236, 256, 288, 332, 384, 405, 430, 486, 495, 498, 524, 530, 601, 613, 625, 872}.

%C If c=1.6 the sequence is just {7, 13, 20, 28, 33, 57, 109}.

%C If c=3/2 the sequence has but one term, 33.

%D P. Ribenboim, The New Book of Prime Number Records, Springer-Verlag, NY, 1995, page 248.

%t t = {}; Do[ If[ PrimePi[ Prime[n + 1]^2] - PrimePi[ Prime[n]^2] < 9n/5, AppendTo[t, n]], {n, 10^5}]; t

%Y Cf. A029707.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Feb 21 2006