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 A174275 #23 Oct 02 2023 16:20:45 %S A174275 0,0,1,0,1,0,1,0,1,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,1,0,1,0,1,0,1,0,0,0, %T A174275 0,0,1,0,0,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,0,0,0,0,1,0,1,0,0,0,0,0,1,0, %U A174275 0,0,1,0,1,0,0,0,0,0,1,0,1,0,1,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,1,0,1,0,0 %N A174275 a(n) = 2^(n-1) mod M(n) where M(n) = A014963(n) is the exponential of the Mangoldt function. %C A174275 Appears to be always either 0 or 1. %C A174275 This follows from Fermat's Little Theorem. - _Charles R Greathouse IV_, Feb 13 2011 %C A174275 Characteristic function for odd prime powers (larger than one). - _Antti Karttunen_, Sep 14 2017, after _Charles R Greathouse IV_'s Feb 13 2011 formula. %H A174275 Antti Karttunen, <a href="/A174275/b174275.txt">Table of n, a(n) for n = 1..16385</a> %H A174275 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a> %F A174275 a(n) = A000079(n-1) mod A014963(n). %F A174275 a(n) = 1 if n = p^k for k > 0 and p a prime not equal to 2, a(n) = 0 otherwise. - _Charles R Greathouse IV_, Feb 13 2011 %t A174275 a[n_] := Mod[2^(n - 1), Exp[MangoldtLambda[n]]] (* _Steven Foster Clark_, Sep 04 2023 *) %o A174275 (PARI) vector(70, n, ispower(k=n, , &k); isprime(k)&k!=2) \\ _Charles R Greathouse IV_, Feb 13 2011 %Y A174275 Cf. A062173. %K A174275 nonn,easy %O A174275 1,1 %A A174275 _Mats Granvik_, Mar 14 2010 %E A174275 More terms from _Antti Karttunen_, Sep 14 2017 %E A174275 Name corrected by _Steven Foster Clark_, Sep 05 2023