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 A346567 #8 Jul 24 2021 04:24:39 %S A346567 341,561,645,1105,2047,4369,4681,5461,8481,16705,33153,266305,278545, %T A346567 526593,1052929,1082401,1398101,2113665,2162721,2290641,4259905, %U A346567 6242685,7674967,8388607,16843009,17895697,22369621,34603041,67371265,268505089,280885153,285212689 %N A346567 Fermat pseudoprimes to base 2 that are palindromic in base 2. %C A346567 There are 133 terms below 2^64. Only 4 of them are also Carmichael numbers (561, 1105, 278545 and 67371265). %H A346567 Amiram Eldar, <a href="/A346567/b346567.txt">Table of n, a(n) for n = 1..133</a> %e A346567 341 is a term since 341 = 101010101_2 is palindromic in base 2, it is composite (= 11 * 31) and 2^340 == 1 (mod 341). %t A346567 pspQ[n_] := CompositeQ[n] && PowerMod[2, n-1, n] == 1; Select[Range[10^6], PalindromeQ[IntegerDigits[#, 2]] && pspQ[#] &] %Y A346567 Intersection of A001567 and A006995. %Y A346567 A065341 and A281576 are subsequences. %Y A346567 Cf. A016041, A068445. %K A346567 nonn,base %O A346567 1,1 %A A346567 _Amiram Eldar_, Jul 23 2021