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 A379496 #17 Jan 05 2025 22:35:32
%S A379496 2,4,3,4,13,15,5,-16,16,35,33,59,103,189,-3,-188,31,-44,53,-55,123,
%T A379496 225,75,89,216,451,315,385,1153,2037,11,-2284,-171,23,-5,-4160,193,
%U A379496 225,69,-247,271,-1599,453,819,1339,2499,141,-309,422,312,605,65,2143,4239,979,1985,2673,5993,5003,2275,15013,29991,-165
%N A379496 a(n) = A019565(1+n) - A019565(A001065(n)), where A019565 is the base-2 exp-function, and A001065 is the sum of proper divisors of n.
%H A379496 Antti Karttunen, <a href="/A379496/b379496.txt">Table of n, a(n) for n = 1..32768</a>
%H A379496 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.
%H A379496 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A379496 a(n) = A019565(1+n) - A379495(n).
%F A379496 For even n, a(n) = 2*A019565(n) - A379495(n).
%F A379496 For n of the form 4k+1, a(n) = (3/2)*A019565(n) - A379495(n).
%o A379496 (PARI)
%o A379496 A019565(n) = { my(m=1, p=1); while(n>0, p = nextprime(1+p); if(n%2, m *= p); n >>= 1); (m); };
%o A379496 A379496(n) = (A019565(1+n) - A019565(sigma(n)-n));
%Y A379496 Cf. A001065, A019565, A379495, A379501 [= a(A016754(n))].
%Y A379496 Cf. also A379498.
%K A379496 sign
%O A379496 1,1
%A A379496 _Antti Karttunen_, Jan 05 2025