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 A236959 #20 Mar 21 2025 18:17:35 %S A236959 1,2,4,2,10,4,16,6,22,28,10,12,40,14,46,52,58,20,22,70,24,26,82,88,32, %T A236959 100,34,106,36,112,42,130,136,46,148,50,52,54,166,172,178,60,190,64, %U A236959 196,66,70,74,226,76,232,238,80 %N A236959 Number of nonzero cubic residues modulo the n-th prime. %F A236959 If prime(n)-1 = 3k then a(n) = k otherwise a(n) = prime(n)-1. %F A236959 a(n) = A006093(n)/gcd(A006093(n),3). - _Ridouane Oudra_, Mar 13 2025 %e A236959 a(4) = 2 for residues of x^3 (mod 7 = prime(4)) are 1 and 6. %e A236959 a(3) = 4 for residues of x^3 (mod 5 = prime(3)) are 1, 2, 3, 4. %p A236959 seq((ithprime(n)-1)/gcd(3,ithprime(n)-1), n=1..80); # _Ridouane Oudra_, Mar 13 2025 %Y A236959 Cf. A130290, A000040. %K A236959 nonn %O A236959 1,2 %A A236959 _Carmine Suriano_, Apr 22 2014 %E A236959 a(20) corrected by _Ridouane Oudra_, Mar 13 2025