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 A329026 #15 Feb 21 2025 08:22:10 %S A329026 12,14,2127,1232495490 %N A329026 Numbers k such that k = Product(p_j^e_j) = concatenation(pi(p_j)), where pi = A000720. %C A329026 Numbers k such that k equals concatenation of indices of distinct prime factors of k, in increasing order. %C A329026 Fixed points of A329025. %C A329026 No other terms below 10^17. - _Max Alekseyev_, Feb 21 2025 %H A329026 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a> %e A329026 2127 is a term because 2127 = 3 * 709 = prime(2) * prime(127) = concat(2, 127). %t A329026 a[n_] := FromDigits[Flatten@IntegerDigits@(PrimePi[#[[1]]] & /@ FactorInteger[n])]; Select[Range[2200], a[#] == # &] %Y A329026 Cf. A000720, A329025. %K A329026 nonn,base,more %O A329026 1,1 %A A329026 _Ilya Gutkovskiy_, Nov 02 2019 %E A329026 a(4) from _Giovanni Resta_, Nov 04 2019