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 A069619 #5 May 21 2025 19:00:54 %S A069619 7,71,271,2711,52711,5271121,135271121,1352711219,271352711219, %T A069619 27135271121911,1227135271121911,122713527112191161, %U A069619 20122713527112191161,20122713527112191161109,2720122713527112191161109 %N A069619 a(1) = 7; a(2n) = smallest prime that is a right concatenation of a(2n-1) and a number with no insignificant zeros and a(2n+1) = smallest prime ending in ( the least significant digits) a(2n-1). Alternate left and right concatenation yielding primes. %e A069619 a(4) = 2711 starting with a(3) = 271 and a(5) = 52711 in a(4) = 2711. %Y A069619 Cf. A053582, A069605, A069606, A069607, A069608, A069609, A069610, A069611, A069613, A069614, A069615, A069616, A069617, A069618. %K A069619 nonn,base %O A069619 1,1 %A A069619 _Amarnath Murthy_, Mar 27 2002 %E A069619 More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Mar 30 2003