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 A231278 #13 Oct 23 2022 10:28:11 %S A231278 2,111,212,1011,1101,1121,2012,2122,10121,10211,11001,11201,12011, %T A231278 12121,12211,20012,20102,20122,21002,21022,22102,22122,22212,101001, %U A231278 101021,101111,102101,102121,110021,110111,110221,111121,111211,112001,112201,120011,120121 %N A231278 Not necessarily palindromic primes of which initial and terminal digits are identical, as written in base 3. %C A231278 Base-3 analog of what A077652 is for base 10. %H A231278 Harvey P. Dale, <a href="/A231278/b231278.txt">Table of n, a(n) for n = 1..2500</a> %e A231278 a(3) = 212, which starts and ends with "2", and in base 3 means 2*(3^2) + 1*(3^1) + 2*(3^0) = 18 + 3 + 2 = 23 (base 10), which is prime. %t A231278 FromDigits/@Select[IntegerDigits[#,3]&/@Prime[Range[100]],#[[1]]==#[[-1]]&] (* _Harvey P. Dale_, Oct 23 2022 *) %Y A231278 Cf. A000030, A000040, A007089, A077652, A227858. %K A231278 nonn,base,easy %O A231278 1,1 %A A231278 _Jonathan Vos Post_, Nov 06 2013 %E A231278 More terms from _Alois P. Heinz_, Nov 07 2013