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 A057692 #24 May 31 2025 18:37:00
%S A057692 2,31,641,12422153,66132153133
%N A057692 Smallest prime which produces exactly n+1 different primes after n applications of the A048376 transform.
%C A057692 a(4) found by _Carlos Rivera_ and confirmed to be the smallest by Paul Jobling (Paul.Jobling(AT)WhiteCross.com)
%C A057692 a(5) = 66132153133 leads to a final (probable) prime of 3560 digits. If zero is allowed, then a(5) = 12505785661 and the last (probable) prime would have 10982 digits. - _Giovanni Resta_, Sep 15 2011
%H A057692 C. Rivera (Ed.), <a href="http://www.primepuzzles.net/puzzles/puzz_112.htm">Puzzle 112. Automorphic primes</a>, primepuzzles.net. (Published Oct. 2000 or earlier.)
%e A057692 31 becomes 3331 and both 31 and 3331 are primes. 641 becomes 66666644441 and then 66666666666666666666666666666666666644444444444444441 and all 3 are primes.
%o A057692 (PARI) A057692(n,s=2)={ forprime(p=s,, my(q=p); for(i=2,n, isprime(q=A048376(q))||next(2)); isprime(A048376(q))||return(p))} \\ Impractical for n>3. - _M. F. Hasler_, Jan 23 2013
%Y A057692 a(1,2,3,...) is a subsequence of A057628.
%K A057692 base,hard,nonn,more
%O A057692 0,1
%A A057692 _G. L. Honaker, Jr._, Oct 20 2000
%E A057692 a(5) from _Giovanni Resta_, Sep 15 2011
%E A057692 Definition corrected by _M. F. Hasler_, Jan 23 2013