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 A168008 #10 Mar 15 2023 03:58:23 %S A168008 1,2,-1,3,-1,5,-1,3,-1,11,-1,3,-1,23,-1,3,-1,47,-1,3,-1,5,-1,3,-1,101, %T A168008 -1,3,-1,7,-1,11,-1,3,-1,13,-1,233,-1,3,-1,467,-1,3,-1,5,-1,3,-1,941, %U A168008 -1,3,-1,7,-1,1889,-1,3,-1,3779,-1,3,-1,7559,-1,3,-1,13,-1 %N A168008 First differences of A168007. %o A168008 (Python) %o A168008 from itertools import count, islice %o A168008 from sympy import primefactors %o A168008 def A168008_gen(): # generator of terms %o A168008 a = 1 %o A168008 for n in count(2): %o A168008 yield (b:=min(primefactors(a),default=1) if a&1 or a==2 else -1) %o A168008 a += b %o A168008 A168008_list = list(islice(A168008_gen(),20)) # _Chai Wah Wu_, Mar 14 2023 %Y A168008 Cf. A168007, A168009. %K A168008 sign %O A168008 1,2 %A A168008 _Omar E. Pol_, Nov 19 2009 %E A168008 More terms from _Jinyuan Wang_, Mar 14 2020