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 A157657 #22 May 03 2025 22:25:17 %S A157657 1,1,1,0,1,-1,1,0,0,-1,1,0,1,-1,-1,0,1,0,1,0,-1,-1,1,0,0,-1,0,0,1,1,1, %T A157657 0,-1,-1,-1,0,1,-1,-1,0,1,1,1,0,0,-1,1,0,0,0,-1,0,1,0,-1,0,-1,-1,1,0, %U A157657 1,-1,0,0,-1,1,1,0,-1,1,1,0,1,-1,0,0,-1,1,1,0,0,-1,1,0,-1,-1,-1,0,1,0,-1,0,-1,-1,-1,0,1,0,0,0 %N A157657 a(1) = 1, a(n) = -mu(n) for n >= 2. %C A157657 Apparently the Dirichlet inverse of A114006. [_R. J. Mathar_, Jul 15 2010] %C A157657 Not multiplicative; for example a(2)*a(3) != a(6). - _R. J. Mathar_, Mar 31 2012 %H A157657 Antti Karttunen, <a href="/A157657/b157657.txt">Table of n, a(n) for n = 1..5000</a> %H A157657 <a href="/index/Eu#epf">Index entries for sequences computed from exponents in factorization of n</a> %t A157657 a[1]:=1; a[n_]:=-MoebiusMu[n]; Array[a,100] (* _Stefano Spezia_, May 03 2025 *) %o A157657 (PARI) a(n)=if(n==1,1, -moebius(n)); \\ _Joerg Arndt_, Aug 25 2014 %o A157657 (Scheme) (define (A157657 n) (if (= 1 n) 1 (- (A008683 n)))) ;; _Antti Karttunen_, Jul 26 2017 %Y A157657 Cf. A008683, A157658 (same except for a(1)). %K A157657 sign %O A157657 1,1 %A A157657 _Jaroslav Krizek_, Mar 03 2009 %E A157657 Added more terms, _Joerg Arndt_, Aug 25 2014