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 A088606 #27 Jul 16 2021 06:38:50 %S A088606 0,1,0,1,2,1,3,4,2,2,1,1,2,4,3,3,3,4,1,2,1,1,2,3,1,5,1,5,1,2,4,2,2,4, %T A088606 11,1,4,1,3,6,2,1,3,1,5,6,4,1,5,1,5,2,4,2,3,6,2,3,1,2,1,2,1,2,3,6,3,4, %U A088606 2,4,6,3,1,1,6,2,2,4,12,1,5,4,5,1,1,5,3,3,3,3,2,5,1,3,1,2,17,2,1,3,3,2,5,5 %N A088606 Smallest number k such that concatenation of k and prime(n) is a prime, or 0 if no other number exists. a(1) = a(3) = 0. %C A088606 Subsidiary sequences: (set(1)) Index of the start of the first occurrence of a string of n consecutive 1's or 2's or 3's etc. (set (2)): a(n) = smallest prime such that concatenation of 1 with n successive primes starting from a(n) gives primes in each case. (n primes are obtained.) Similarly for 2, 3, etc. Conjecture: The subsidiary sequences are infinite. %C A088606 A065112(n) = a(n) concatenated with prime(n). - _Bill McEachen_, May 27 2021 %o A088606 (PARI) a(n) = if ((n==1) || (n==3), 0, my(k=1); while (!isprime(eval(Str(k, prime(n)))), k++); k); \\ _Michel Marcus_, Jul 11 2021 %Y A088606 Cf. A096915, A065112. %K A088606 base,nonn %O A088606 1,5 %A A088606 _Amarnath Murthy_, Oct 15 2003 %E A088606 More terms from _Ray Chandler_, Oct 18 2003