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 A248947 #16 Apr 09 2021 19:05:01
%S A248947 3,1,3,2,7,9,9,3,6,2,8,1,8,0,0,5,2,2,6,7,2,0,0,3,4,0,1,2,8,5,8,5,6,7,
%T A248947 6,3,8,0,5,2,2,8,0,5,2,2,4,1,8,8,7,2,4,0,1,1,2,7,1,9,2,0,0,4,1,8,0,5,
%U A248947 4,4,3,7,2,3,1,9,8,2,3,3,8,7,1,5,9,3,5,4,5,4,9,3,6,5,3,7,9,6,2,9,4,8,9,5,7
%N A248947 Decimal expansion of Sum_{n >= 1} tan(1/n)^2.
%H A248947 Vaclav Kotesovec, <a href="/A248947/b248947.txt">Table of n, a(n) for n = 1..500</a>
%e A248947 3.132799362818005226720034012858567638052280522418872401127192004180544...
%p A248947 evalf(sum((tan(1/n))^2, n=1..infinity), 120); # _Vaclav Kotesovec_, Oct 20 2014
%t A248947 (* N[Sum[Tan[1/n]^2, {n, 1, Infinity}], 120], yields only 25 correct decimals *)
%o A248947 (PARI) default(realprecision,120); sumpos(n=1,(tan(1/n))^2) \\ _Vaclav Kotesovec_, Oct 20 2014
%Y A248947 Cf. A248945, A248946, A248948.
%K A248947 nonn,easy,cons
%O A248947 1,1
%A A248947 _Clark Kimberling_, Oct 18 2014