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 A080356 #13 Aug 22 2021 19:04:57
%S A080356 0,1,2,1,1,1,1,1,2,2,2,1,1,1,2,2,2,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
%T A080356 2,3,3,3,3,3,3,2,2,2,2,2,2,2,2,2,3,3,3,4,4,4,4,4,4,3,3,3,3,3,3,3,3,3,
%U A080356 4,4,4,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,6,6,6,7,7,7,6,6,6,6
%N A080356 Number of twin primes between n and 2n: a(n) = number of j in range n <= j <= 2*n such that j and j+2 are primes.
%H A080356 T. D. Noe, <a href="/A080356/b080356.txt">Table of n, a(n) for n=1..10000</a>
%e A080356 n=36: between 36 and 72 the primes p such that (p,p+2) is a pair of twin primes are {41,59,71}, so a(36)=3.
%t A080356 Table[Count[Table[PrimeQ[j]&&PrimeQ[j+2], {j, n, 2*n}], True], {n, 1, 1000}]
%Y A080356 Cf. A001359, A071538.
%K A080356 nonn
%O A080356 1,3
%A A080356 _Labos Elemer_, Feb 19 2003
%E A080356 Definition clarified by _N. J. A. Sloane_, Aug 22 2021