This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A099261 #4 Mar 30 2012 17:36:43
%S A099261 2,5,10,13,17,21,24,28,31,35,38,42,45,49,52,56,59,62,66,69,73,76,79,
%T A099261 83,86,89,93,96,100,103,106,110,113,116,120,123,127,130,133,137,140,
%U A099261 143,147,150,153,157,160,163,167,170,173,177,180,184,187,190,194,197,200,204
%N A099261 Length in bits of (10^n)-th prime number.
%H A099261 Pierre Dusart, <a href="http://arxiv.org/abs/1002.0442">Estimates of Some Functions Over Primes Without R.H.</a>
%e A099261 a(1) = 5 because A006988(1) = prime(10^1) = 29 = 11101 (base 2) has five bits.
%o A099261 (PARI) a(n)=if(n<3,return([2,5,10][n+1]));my(l=n*log(10),ll=log(l),x=n*log(10)/log(2),lb=ceil(x+log(l+ll-1+(ll-2.2)/l)/log(2)),ub=ceil(x+log(l+ll-1+(ll-2)/l)/log(2)));if(lb==ub,lb,error("Cannot determine a("n")"))
%Y A099261 Cf. A006988 ((10^n)-th prime), A006880 (pi(10^n)), A007053 (pi(2^n)), A099260 (decimal digit lengths).
%K A099261 nonn,base
%O A099261 0,1
%A A099261 _Rick L. Shepherd_, Oct 11 2004
%E A099261 Extension, program, and reference from _Charles R Greathouse IV_, Aug 03 2010