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 A077815 #9 Dec 04 2021 15:01:47 %S A077815 0,2,4,4,16,4,15,16,64,16,56,16,40,64,31,0,222,64,58,256,127,56,392, %T A077815 256,451,40,433,176,30,256,187,0,958,800,841,208,38,780,586,1536,944, %U A077815 568,1076,1200,91,392,2069,1024,2157,1076,1021,1600,1909,2620,826,2752 %N A077815 2^phi(n) mod n^2, where phi is Euler's totient function A000010. %H A077815 Harvey P. Dale, <a href="/A077815/b077815.txt">Table of n, a(n) for n = 1..1000</a> %e A077815 a(42) = 2^phi(42) mod 42*42 = 2^phi(2*3*7) mod 1764 = 2^(42*(1-1/2)*(1-1/3)*(1-1/7)) mod 1764 = 2^12 mod 1764 = 4096 mod 1764 = 568. %t A077815 PowerMod[2,EulerPhi[#],#^2]&/@Range[60] (* _Harvey P. Dale_, Dec 04 2021 *) %o A077815 (PARI) a(n)=lift(Mod(2,n^2)^eulerphi(n)) \\ _Charles R Greathouse IV_, Feb 21 2013 %Y A077815 Cf. A077816, A000010, A000290. %K A077815 nonn %O A077815 1,2 %A A077815 _Reinhard Zumkeller_, Nov 17 2002