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 A368625 #12 Feb 16 2025 08:34:06
%S A368625 0,0,1,1,1,1,1,0,0,1,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,1,
%T A368625 1,0,1,1,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,1,1,1,1,1,
%U A368625 1,1,1,0,1,1,1,1,1,1,1,0,1,1,1,0,1,1,1,0,1,1,1,1,1,1,1,0,1,1,1,1,1,1,1,0,1
%N A368625 Characteristic function of non-refactorable numbers (A159973).
%H A368625 Antti Karttunen, <a href="/A368625/b368625.txt">Table of n, a(n) for n = 1..100000</a>
%H A368625 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RefactorableNumber.html">Refactorable Number</a>
%H A368625 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F A368625 a(n) = ceiling(n/d(n))-floor(n/d(n)), where d(n) is the number of divisors of n (A000005).
%F A368625 a(n) = 1 - A336040(n).
%F A368625 a(n) = [A054008(n) > 0], where [ ] is the Iverson bracket. - _Antti Karttunen_, Jan 17 2025
%t A368625 Table[(Ceiling[n/DivisorSigma[0, n]] - Floor[n/DivisorSigma[0, n]]), {n, 100}]
%o A368625 (PARI) A368625(n) = !!(n%numdiv(n)); \\ _Antti Karttunen_, Jan 17 2025
%Y A368625 Cf. A000005, A033950 (refactorable numbers), A054008, A159973, A336040.
%K A368625 nonn,easy
%O A368625 1,1
%A A368625 _Wesley Ivan Hurt_, Jan 01 2024
%E A368625 Data section extended up to a(105) by _Antti Karttunen_, Jan 17 2025