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 A225544 #6 May 13 2013 00:52:42 %S A225544 2,29,23,347,293,239,57487,486193,1725121513,1221261395831, %T A225544 28549657193411 %N A225544 a(n) begins the earliest chain of exactly n distinct primes such that any term in the chain equals the previous term increased by the product of its digits. %C A225544 A chain ends either at a composite number, or at a prime which contains a zero, since the subsequent primes in the chain are identical. %e A225544 23 starts the earliest chain of length 3, since 23+2*3 = 29, 29+2*9 = 47 and 47+4*7 = 75, where the first 3 terms are distinct and prime, so a(3) = 23. The last distinct term in the chain starting at 1725121513 is the prime 1725980623 which contains a zero and thus generates itself. %t A225544 seq = 0*Range[8]; p = 2; While[p < 500000, v = Length@ NestWhileList[# + Times @@ IntegerDigits@# &, p, PrimeQ@#2 && #1 != #2 &, 2] - 1; If[ seq[[v]] == 0, seq[[v]] = p]; p = NextPrime@p]; seq %Y A225544 Cf. A090009, A145280. %K A225544 nonn,base %O A225544 1,1 %A A225544 _Giovanni Resta_, May 10 2013