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 A290051 #22 Aug 08 2017 22:04:19
%S A290051 6,2,294,2,126,112,310,14,150,840,3200,98,45360,10500,57120,40320,
%T A290051 242250,9548,21839790,3756480,200425680,678810,1359540
%N A290051 Least k > 1 such that the set of distinct prime divisors of k is equal to the set of distinct prime divisors of sigma_n(k) where sigma_n (k) is result of applying sum-of-divisors function n times to k.
%C A290051 a(24) > 10^9.
%e A290051 a(3) = 294 because sigma(sigma(sigma(2*3*7^2))) = 2^5*3*7^2 and 2*3*7^2 = 294 is the least number with this property.
%t A290051 f[n_] := Block[{k = 2}, While[ Transpose[ FactorInteger[ Nest[ DivisorSigma[1, #] &, k, n]]][[1]] != Transpose[ FactorInteger[ k]][[1]], k += 2]; k]; (* _Robert G. Wilson v_, Aug 03 2017 *)
%Y A290051 Cf. A000203, A027598.
%K A290051 nonn,more
%O A290051 1,1
%A A290051 _Altug Alkan_, Aug 03 2017
%E A290051 a(10)-a(23) from _Giovanni Resta_, Aug 03 2017