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 A297363 #10 Sep 08 2021 21:14:35 %S A297363 1,4,13,16,22,40,46,56,94,104,121,160,364,526,862,968,1093,1312,1514, %T A297363 3146,3194,3280,3742,4376,5368,7280,7702,8744,9841,28418,29524,40880, %U A297363 69022,75920,88573,106288,157394 %N A297363 Numbers k such that (3^ord(3, k) - 1)/k is prime, where ord(3, k) is the multiplicative order of 3 (mod k). %C A297363 The corresponding primes are 2, 2, 2, 5, 11, 2, 3851, 13, 1001523179, 7, 2, 41, 2, 605199588591144003100881306574406851660288427740394885828171, ... %e A297363 46 is in the sequence since ord(3, 46) = 11 and (3^11 - 1)/46 = 3851 is prime. %t A297363 aQ[n_] := PrimeQ[(3^MultiplicativeOrder[3, n] - 1)/n]; Select[ Range[10000], aQ ] %o A297363 (PARI) isok(n) = (gcd(n,3) == 1) && isprime((3^znorder(Mod(3, n)) - 1)/n); \\ _Michel Marcus_, Dec 30 2017 %Y A297363 Cf. A050975, A053446. %K A297363 nonn,more %O A297363 1,2 %A A297363 _Amiram Eldar_, Dec 29 2017