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 A336656 #12 Jul 29 2020 06:20:55 %S A336656 1,2,4,7,8,11,13,14,22,23,26,28,31,43,44,46,47,49,52,56,59,61,62,67, %T A336656 71,77,79,83,86,88,91,92,94,98,103,104,107,118,121,122,124,131,134, %U A336656 139,142,143,154,157,158,161,166,167,169,172,179,182,184,188,191,196 %N A336656 Numbers k not divisible by 3 such that the multiplicative order of 3 modulo k is squarefree. %H A336656 Amiram Eldar, <a href="/A336656/b336656.txt">Table of n, a(n) for n = 1..10000</a> %H A336656 Francesco Pappalardi, <a href="https://www.emis.de/journals/NYJM/nyjm/NYJM/j/2003/9-17.html">Square free values of the order function</a>, New York J. Math., Vol. 9 (2003), pp. 331-344. %F A336656 The number of terms not exceeding x is (a + o(1))* x * log(x)^(b-1), where a and b (~ 0.51175) are constants (Pappalardi, 2003). %e A336656 2 is a term since the multiplicative order of 3 modulo 2 is 1 which is squarefree. %t A336656 Select[Range[200], !Divisible[#, 3] && SquareFreeQ[MultiplicativeOrder[3, #]] &] %o A336656 (PARI) isok(k) = (k % 3) && issquarefree(znorder(Mod(3,k))); \\ _Michel Marcus_, Jul 29 2020 %Y A336656 Cf. A007734, A005117, A049149, A336654, A336655. %K A336656 nonn %O A336656 1,2 %A A336656 _Amiram Eldar_, Jul 28 2020