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 A120905 #13 Sep 16 2015 05:01:27
%S A120905 1,-3,-7,-527,164833,-98248054847,-3977703802948722503807,
%T A120905 -510456831154766758152181998159655209453904127
%N A120905 Real part of (1 + 2i)^(2^n) where i is sqrt(-1).
%C A120905 The next term a(8) has 90 digits and is too large to be displayed here.
%F A120905 a(n) = A006495(2^n).
%F A120905 a(n) = real part of (2 + sqrt(-1))^(2^n) for n >= 0.
%e A120905 a(3) = -527 since (1 + 2i)^8 = (-527 + 336i) = A006495(8).
%p A120905 a:= n-> Re((1 + 2*I)^(2^n));
%p A120905 seq (a(n), n=0..10);
%t A120905 Table[Re[(1 + 2I)^(2^n)], {n, 0, 8}] (* _Stefan Steinerberger_, Jul 23 2006 *)
%Y A120905 Cf. A006495.
%K A120905 sign
%O A120905 0,2
%A A120905 _Gary W. Adamson_, Jul 14 2006
%E A120905 Corrected and extended by _Stefan Steinerberger_ and _Emeric Deutsch_, Jul 23 2006