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 A367515 #10 Nov 23 2023 12:28:14 %S A367515 1,2,2,2,2,4,2,1,2,4,2,4,2,4,4,2,2,4,2,4,4,4,2,2,2,4,1,4,2,8,2,1,4,4, %T A367515 4,4,2,4,4,2,2,8,2,4,4,4,2,4,2,4,4,4,2,2,4,2,4,4,2,8,2,4,4,1,4,8,2,4, %U A367515 4,8,2,2,2,4,4,4,4,8,2,4,2,4,2,8,4,4,4 %N A367515 The number of unitary divisors of n that are exponentially odious numbers (A270428). %H A367515 Amiram Eldar, <a href="/A367515/b367515.txt">Table of n, a(n) for n = 1..10000</a> %F A367515 Multiplicative with a(p^e) = A001285(e). %F A367515 a(n) = A034444(n)/A367516(n). %F A367515 a(n) = 2^A293439(n). %F A367515 a(n) >= 1, with equality if and only if n is an exponentially evil number (A262675). %F A367515 a(n) <= A034444(n), with equality if and only if n is an exponentially odious number (A270428). %t A367515 f[p_, e_] := If[OddQ[DigitCount[e, 2, 1]], 2, 1]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] %o A367515 (PARI) a(n) = vecprod(apply(x -> hammingweight(x)%2+1, factor(n)[, 2])); %o A367515 (Python) %o A367515 from sympy import factorint %o A367515 def A367515(n): return 1<<sum(1 for e in factorint(n).values() if e.bit_count()&1) # _Chai Wah Wu_, Nov 23 2023 %Y A367515 Cf. A001285, A262675, A270428, A293439. %Y A367515 Similar sequences: A034444, A055076, A056624, A366901, A366902, A367516. %K A367515 nonn,easy,mult %O A367515 1,2 %A A367515 _Amiram Eldar_, Nov 21 2023