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 A134070 #18 Jul 17 2025 08:24:12
%S A134070 13,13471118294776123,
%T A134070 134711182947761231993225218431364220735715778934915127244763960364079103682167761271443439204710647114985118604983010349
%N A134070 Primes in A130774.
%C A134070 A130774 = {1, 13, 134, 1347, 134711, 13471118, 1347111829, 134711182947, 13471118294776, 13471118294776123, ...} = Concatenate Lucas numbers. Indices of prime terms in A130774 are {2, 10, 31, ...}.
%C A134070 a(4) > A130774(500) = 1.347...*10^26425, if it exists. - _Amiram Eldar_, Jul 17 2025
%H A134070 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LucasNumber.html">Lucas Number</a>.
%H A134070 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SmarandacheSequences.html">Smarandache Sequences</a>.
%e A134070 a(1) = A130774(2) = 13.
%e A134070 a(2) = A130774(10) = 13471118294776123.
%e A134070 a(3) = A130774(31) = 13471118294776123199322521843136422073571577893491512724476396036407910368216776127144343920471064711498511860498301034.
%t A134070 Select[Module[{nn=40,ll},ll=LucasL[Range[nn]];Table[FromDigits[Flatten[IntegerDigits/@Take[ll,n]]],{n,nn}]],PrimeQ] (* _Harvey P. Dale_, May 07 2023 *)
%Y A134070 Cf. A000204 (Lucas numbers).
%Y A134070 Cf. A130774 (concatenation of Lucas numbers).
%Y A134070 Cf. A019523 (concatenation of Fibonacci numbers).
%Y A134070 Cf. A038399 (concatenation of first n nonzero Fibonacci numbers in reverse order).
%Y A134070 Cf. A134072 (concatenation of A000204 Lucas numbers (beginning at 1) in reverse order).
%Y A134070 Cf. A134069 (primes in A038399).
%Y A134070 Cf. A134071 (primes in A134072).
%K A134070 nonn,base,bref,hard
%O A134070 1,1
%A A134070 _Alexander Adamchuk_, Oct 06 2007
%E A134070 Edited by _Charles R Greathouse IV_, Apr 24 2010