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 A321340 #19 Nov 26 2018 17:01:47
%S A321340 1,2,18,68664550781250
%N A321340 a(1) = 1; thereafter a(n) = a(n-1) * prime(n-1)^a(n-1).
%C A321340 The prime factorization of a(n) describes all previous terms in the sequence: a(n) = prime(1)^a(1) * prime(2)^a(2) * prime(3)^a(3) * ...* prime(n-1)^a(n-1).
%C A321340 An infinite and monotonically increasing sequence which grows very rapidly.
%e A321340 68664550781250 = 2 * 3^2 * 5^18 = prime(1)^1 * prime(2)^2 * prime(3)^18.
%t A321340 Nest[Append[#, #[[-1]] Prime[Length@ #]^#[[-1]] ] &, {1}, 3] (* _Michael De Vlieger_, Nov 05 2018 *)
%o A321340 (PARI) apply( ppp(n) = prod(i=1, n-1, prime(i)^ppp(i)), [1..4] )
%Y A321340 Somewhat similar to A007097.
%Y A321340 Cf. A321339.
%K A321340 nonn
%O A321340 1,2
%A A321340 _Russell Y. Webb_, Nov 05 2018