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 A225855 #15 Apr 23 2022 09:42:42 %S A225855 -1,-1,3,-1,5,9,-7,-1,27,25,11,162,13,49,521,-1,697,2196,19,625,8435, %T A225855 121,-23,59049,3120,169,177147,2401,29,982635,-237367,-1,3958307, %U A225855 781745,121691,28697814,37,361,89405461,1953125 %N A225855 Difference between the number of nonnegative evil and odious multiples of n less than 2^n. %C A225855 It appears that for n = 2^i*p, i>0, p prime, a(n) = p^(2^i) or a multiple of it. %C A225855 For which n is a(n) negative? %C A225855 For prime n and related conjectures, see A133954. %o A225855 (PARI) a(n)=sum(i=0,floor(2^n/n),subst(Pol(binary(i*n)),x,1)%2==0)-sum(i=0,floor(2^n/n),subst(Pol(binary(i*n)),x,1)%2) %Y A225855 Cf. A000069, A001969, A133954. %K A225855 sign,hard,more %O A225855 1,3 %A A225855 _Ralf Stephan_, Aug 31 2013 %E A225855 a(31)-a(40) from _Amiram Eldar_, Apr 23 2022