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 A057943 #14 Apr 03 2023 10:36:09 %S A057943 2,51,60,75,96,200,207,279,288,348,402,432,464,492,500,531,555,590, %T A057943 646,652,662,675,695,732,750,790,843,855,860,888,894,920,927,983,984, %U A057943 1074,1102,1139,1140,1150,1152,1163,1164,1203,1215,1230,1251,1278,1283,1336 %N A057943 Numbers k such that the smallest palindromic pseudoprime to base k is 101101. %H A057943 Amiram Eldar, <a href="/A057943/b057943.txt">Table of n, a(n) for n = 1..10000</a> %H A057943 C. K. Caldwell, <a href="https://t5k.org/glossary/page.php?sort=CarmichaelNumber">Carmichael number</a> %H A057943 C. K. Caldwell, <a href="https://t5k.org/glossary/page.php?sort=Pseudoprime">Pseudoprimes</a> %H A057943 C. Rivera, <a href="http://www.primepuzzles.net/problems/prob_024.htm">Carmichael Numbers</a> %H A057943 <a href="/index/Ps#pseudoprimes">Index entries for sequences related to pseudoprimes</a> %e A057943 2 is a term since 101101 is the least Fermat pseudoprime to base 2 (A001567) which is also a palindrome in base 10 (A002113). %e A057943 3 is not a term since the least Fermat pseudoprime to base 3 (A005935) which is also a palindrome in base 10 is 121. %t A057943 palinComps = Select[Range[2, 101100], PalindromeQ[#] && CompositeQ[#] &]; seqQ[n_] := PowerMod[n, 101100, 101101] == 1 && AllTrue[palinComps, PowerMod[n, #-1, #] != 1 &]; Select[Range[1336], seqQ] (* _Amiram Eldar_, Jan 30 2020 *) %Y A057943 Cf. A001567, A002113, A002997. %K A057943 nonn,base %O A057943 1,1 %A A057943 _Patrick De Geest_, Oct 15 2000