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 A255771 #14 Aug 04 2016 22:35:30 %S A255771 1,1,1,2,2,1,2,2,4,2,2 %N A255771 Number of distinct prime factors of A220294(n). %C A255771 These are the first differences of A255770. %D A255771 Arthur Engel, Problem-Solving Strategies, Springer, 1998, pages 121-122 (E3, said to be a "recent competition problem from the former USSR"). %H A255771 factordb, <a href="http://factordb.com/index.php?query=1+-+2%5E%282%5E%28n-1%29%29+%2B+2%5E%282%5En%29">First 20 factorizations of A220294</a> %e A255771 A220294(0) = 3 so a(0) = 1. %e A255771 A220294(1) = 13 so a(1) = 1. %e A255771 A220294(2) = 241 so a(2) = 1. %e A255771 A220294(3) = 97*673 so a(3) = 2. %e A255771 A220294(4) = 193*22253377 so a(4) = 2. %Y A255771 Cf. A220161, A220294, A255770, A255772, A275528. %K A255771 nonn,hard,more %O A255771 0,4 %A A255771 _Hans Havermann_, Mar 06 2015 %E A255771 Offset changed by _Arkadiusz Wesolowski_, Aug 01 2016 %E A255771 a(9) was found in 2008 by Geoffrey Reynolds. a(10) was found by Anders Björn and Hans Riesel. - _Arkadiusz Wesolowski_, Aug 02 2016