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 A132800 #24 Aug 11 2020 09:59:34
%S A132800 1,5,2,7,2,6,9,0,2,7,2,5,7,2,2,4,7,1,5,2,8,1,7,5,4,1,8,7,4,4,2,5,9,1,
%T A132800 2,4,3,0,3,4,2,3,6,4,2,7,1,4,6,3,2,9,8,5,0,8,6,2,8,8,3,7,5,3,6,7,3,2,
%U A132800 1,3,2,2,2,3,0,9,2,1,1,0,6,2,7,0,3,7,0,9,5,9,5,5,8,9,8,7,3,9
%N A132800 Decimal expansion of Sum_{n >= 1} 1/3^prime(n).
%C A132800 Equivalently, the real number in (0,1) having the characteristic function of the primes, A010051, as its base-3 expansion. - _M. F. Hasler_, Jul 04 2017.
%H A132800 Vincenzo Librandi, <a href="/A132800/b132800.txt">Table of n, a(n) for n = 0..2000</a>
%F A132800 From _Amiram Eldar_, Aug 11 2020: (Start)
%F A132800 Equals Sum_{k>=1} 1/A057901(k).
%F A132800 Equals 2 * Sum_{k>=1} pi(k)/3^(k+1), where pi(k) = A000720(k). (End)
%e A132800 0.15272690272572247152817541874425912430342364271463298508628837536732...
%t A132800 RealDigits[Sum[1/3^Prime[k], {k, 100}], 10, 100][[1]] (* _Vincenzo Librandi_, Jul 05 2017 *)
%o A132800 (PARI) /* Sum of 1/m^p for primes p */ sumnp(n,m) = { local(s=0,a,j); for(x=1,n, s+=1./m^prime(x); ); a=Vec(Str(s)); for(j=3,100, print1(eval(a[j])",") ) }
%o A132800 (PARI) suminf(n=1,1/3^prime(n)) \\ Then: digits(%\.1^default(realprecision))[1..-3] to remove the last 2 digits. N.B.: Functions sumpos() and sumnum() yield much less accurate results. - _M. F. Hasler_, Jul 04 2017
%Y A132800 Cf. A000720, A051006 (analog for base 2), A132797 (analog for base 5), A010051 (characteristic function of the primes), A057901, A132806 (base 4).
%K A132800 cons,nonn
%O A132800 0,2
%A A132800 _Cino Hilliard_, Nov 17 2007
%E A132800 Offset corrected _R. J. Mathar_, Jan 26 2009
%E A132800 Edited by _M. F. Hasler_, Jul 04 2017