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 A285634 #7 Feb 16 2025 08:33:44
%S A285634 4,8,64,2097152,
%T A285634 3450873173395281893717377931138512726225554486085193277581262111899648
%N A285634 a(1) = 4, a(n) = Product_{d|a(n-1)} d.
%C A285634 Iterating the product-of-divisors function.
%C A285634 The next term is too large to include.
%C A285634 Let a(n) = Product_{d|a(n-1)} d, with a(1) = p^k, p is a prime, k >= 0 and b(n) = b(n-1)*(b(n-1) + 1)/2, with b(1) = k, then a(n) = p^b(n).
%C A285634 The next term has 8067 digits. - _Harvey P. Dale_, Apr 18 2019
%H A285634 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DivisorProduct.html">Divisor Product</a>
%F A285634 a(1) = 4, a(n) = a(n-1)^(A000005(a(n-1))/2).
%F A285634 a(n) = 2^A007501(n-1).
%e A285634 a(1) = 4;
%e A285634 a(2) = 8 because 4 has 3 divisors {1, 2, 4} and 1*2*4 = 8;
%e A285634 a(3) = 64 because 64 has 7 divisors {1, 2, 4, 8, 16, 32, 64} and 1*2*4*8*16*32*64 = 2097152, etc.
%e A285634 ...
%e A285634 a(6) = 2^26796;
%e A285634 a(7) = 2^359026206;
%e A285634 a(8) = 2^64449908476890321;
%e A285634 a(9) = 2^2076895351339769460477611370186681, etc.
%t A285634 RecurrenceTable[{a[1] == 4, a[n] == Sqrt[a[n - 1]]^DivisorSigma[0, a[n - 1]]}, a, {n, 5}]
%t A285634 NestList[Times@@Divisors[#]&,4,4] (* _Harvey P. Dale_, Apr 18 2019 *)
%Y A285634 Cf. A000005, A000079, A007497, A007501, A007955.
%K A285634 nonn,easy
%O A285634 1,1
%A A285634 _Ilya Gutkovskiy_, Apr 23 2017