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 A339971 #8 Dec 27 2020 19:31:39
%S A339971 1,1,1,1,3,3,3,3,5,5,5,5,15,15,15,15,3,3,3,3,9,9,9,9,15,15,15,15,45,
%T A339971 45,45,45,1,1,1,1,3,3,3,3,5,5,5,5,15,15,15,15,3,3,3,3,9,9,9,9,15,15,
%U A339971 15,15,45,45,45,45,9,9,9,9,27,27,27,27,45,45,45,45,135,135,135,135,27,27,27,27,81,81,81,81,135
%N A339971 Odd part of A339821(n).
%F A339971 If 4n = 2^e1 + 2^e2 + ... + 2^ek [e1 ... ek distinct], then a(n) = A057023(e1) * A057023(e2) * ... * A057023(ek).
%F A339971 a(n) = A053575(A019565(2n)) = A336466(A003961(A019565(n))) = A000265(A339821(n)).
%F A339971 a(n) = A339821(n) / A000079(A339822(n)).
%o A339971 (PARI)
%o A339971 A000265(n) = (n>>valuation(n,2));
%o A339971 A339971(n) = { my(m=1, p=2); while(n>0, p = nextprime(1+p); if(n%2, m *= A000265(p-1)); n >>= 1); (m); };
%Y A339971 Cf. A000010, A000265, A003961, A019565, A053575, A057023, A336466, A339821, A339822, A339970.
%Y A339971 Cf. A339972 (quadrisection).
%K A339971 nonn
%O A339971 0,5
%A A339971 _Antti Karttunen_, Dec 26 2020