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 A177882 #27 May 03 2023 09:13:25
%S A177882 1,15,85,771,4369,65535,327685,3342387,16843009,252645135,1431655765,
%T A177882 12884901891,73014444049,1095216660735,5519032976645,56294136361779,
%U A177882 281479271743489,4222189076152335,23925738098196565
%N A177882 Trisection of A001317.
%C A177882 For n>=1, all terms are in A001969.
%C A177882 Or rows of triangle A008287 mod 2 converted to decimal.
%H A177882 Gheorghe Coserea, <a href="/A177882/b177882.txt">Table of n, a(n) for n = 0..200</a>
%F A177882 a(n) = A001317(3*n).
%t A177882 f[n_] := BitXor[n, BitShiftLeft[n, 1]]; Table[Nest[f, 1, x], {x, 0, 54, 3}]
%o A177882 (PARI)
%o A177882 a(n) = subst(lift(Pol(Mod([1, 1, 1, 1], 2), 'x)^n), 'x, 2);
%o A177882 vector(19, n, a(n-1)) \\ _Gheorghe Coserea_, Jun 12 2016
%o A177882 (Python)
%o A177882 def A177882(n): return sum((bool(~(3*n)&3*n-k)^1)<<k for k in range(3*n+1)) # _Chai Wah Wu_, May 02 2023
%Y A177882 Cf. A001317, A001969, A005190, A007318, A008287.
%K A177882 nonn
%O A177882 0,2
%A A177882 _Vladimir Shevelev_, Dec 14 2010
%E A177882 Definition rewritten by _N. J. A. Sloane_, Jan 01 2011