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 A306452 #28 Sep 18 2021 09:05:23 %S A306452 121,726,3751,4961,7381,11011,29161,32791,142901,228811,239701,341341, %T A306452 551881,566401,595441,671671,784201,856801,1016521,1053426,1237951, %U A306452 1335961,1433971,1804231,1916761,2000251,2254351,2446741,2817001,2983981,3078361,3307051,3562361 %N A306452 Pseudoprimes to base 3 that are not squarefree, including the non-coprime pseudoprimes. %C A306452 Numbers k such that 3^k == 3 (mod k) and k is divisible by the square of a Mirimanoff prime (or base-3 Wieferich prime), A014127. %C A306452 A non-coprime pseudoprime in base b is a number k such that b^k == b (mod k) and that gcd(b, k) > 1, and the non-coprime pseudoprime in base 3 (726, 1053426, 6498426, ...) that are not squarefree are listed in A306450 while the others terms in this sequence (121, 3751, 4961, ...) are listed in A244065. So this sequence is the union of A244065 and A306450. %C A306452 Intersection of A122780 and A013929. %H A306452 Amiram Eldar, <a href="/A306452/b306452.txt">Table of n, a(n) for n = 1..1000</a> %e A306452 121 is a term because 3^120 == (3^5)^24 == 1 (mod 121) and 121 = 11^2. %e A306452 Although 3^725 = 243 rather than 1 mod 726, we see that nevertheless 3^726 = 3 mod 726, and since 726 = 2 * 3 * 11^2, 726 is in the sequence. - _Alonso del Arte_, Mar 16 2019 %t A306452 Select[Range[5000], PowerMod[3, #, #] == 3 && MoebiusMu[#] == 0 &] (* _Alonso del Arte_, Mar 16 2019 *) %o A306452 (PARI) forcomposite(n=1, 10^7, if(Mod(3, n)^n==3 && !issquarefree(n), print1(n, ", "))) %Y A306452 Cf. A013929, A014127, A122780, A158358, A244065, A306450. %K A306452 nonn %O A306452 1,1 %A A306452 _Jianing Song_, Feb 17 2019