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 A083989 #10 Jul 03 2024 18:44:33 %S A083989 3,7,17,23,29,31,41,43,53,67,71,83,109,127,139,151,173,179,197,211, %T A083989 229,263,271,281,307,359,463,547,557,569,587,593,673,677,683,691,701, %U A083989 719,727,757,769,823,839,881,883,887,907,937,983,997,1087,1103,1171,1181 %N A083989 Concatenation of prime k and its 10's complement is a prime. %H A083989 Robert Israel, <a href="/A083989/b083989.txt">Table of n, a(n) for n = 1..10000</a> %e A083989 43 belongs to this sequence as 4357 is also a prime. %p A083989 g:= proc(n) local c; c:= 10^(1+ilog10(n))-n; n*10^(1+ilog10(c))+c end proc: %p A083989 select(t -> isprime(t) and isprime(g(t)), [seq(i,i=3..10000,2)]); # _Robert Israel_, Jul 03 2024 %Y A083989 Cf. A083990, A089186. %K A083989 base,nonn %O A083989 1,1 %A A083989 _Amarnath Murthy_, May 23 2003 %E A083989 More terms from _Jason Earls_, Jun 01 2003