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 A273650 #30 Jan 09 2025 02:05:23 %S A273650 0,0,0,0,0,0,0,0,0,0,1,0,8,0,0,0,10,0,7,0,0,20,1,0,0,16,0,0,24,0,21,0, %T A273650 21,32,0,0,31,22,27,0,30,0,31,24,0,22,27,0,0,0,21,28,29,0,45,0,54,4, %U A273650 14,0,49,54,0,0,30,24,64,36,45,0,19,0,67,70,0,32,42,54,37,0,0,18 %N A273650 a(n) = A000594(n) mod n. %H A273650 Seiichi Manyama, <a href="/A273650/b273650.txt">Table of n, a(n) for n = 1..10000</a> %F A273650 a(n) = A000594(n) mod n. %F A273650 From _Amiram Eldar_, Jan 08 2025: (Start) %F A273650 a(A063938(n)) = 0. %F A273650 abs(a(A295654(n))) = 1. (End) %e A273650 tau(10) mod 10 = (-115920) mod 10 = 0, %e A273650 tau(11) mod 11 = 534612 mod 11 = 1. %t A273650 a[n_] := Mod[RamanujanTau[n], n]; Array[a, 100] (* _Amiram Eldar_, Jan 08 2025 *) %o A273650 (PARI) a(n)=ramanujantau(n)%n \\ assumes the GRH; _Charles R Greathouse IV_, May 27 2016 %o A273650 (Python) %o A273650 from sympy import divisor_sigma %o A273650 def A273650(n): return -840*(pow(m:=n+1>>1,2,n)*(0 if n&1 else pow(m*divisor_sigma(m),2,n))+(sum(pow(i,4,n)*divisor_sigma(i)*divisor_sigma(n-i) for i in range(1,m))<<1)) % n # _Chai Wah Wu_, Nov 08 2022 %Y A273650 Cf. A000594, A063938, A295654. %K A273650 nonn %O A273650 1,13 %A A273650 _Seiichi Manyama_, May 27 2016