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%I #12 Nov 06 2019 19:01:59
%S 12,14,2127,1232495490
%N Numbers k such that k = Product (p_j^e_j) = concatenation (pi(p_j)), where pi = A000720.
%C Numbers k such that k equals concatenation of indices of distinct prime factors of k, in increasing order.
%C Fixed points of A329025.
%C a(5) > 2.4*10^11, if it exists. - _Giovanni Resta_, Nov 05 2019
%H <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%e 2127 is a term because 2127 = 3 * 709 = prime(2) * prime(127) = concat(2, 127).
%t a[n_] := FromDigits[Flatten@IntegerDigits@(PrimePi[#[[1]]] & /@ FactorInteger[n])]; Select[Range[2200], a[#] == # &]
%Y Cf. A000720, A329025.
%K nonn,base,more
%O 1,1
%A _Ilya Gutkovskiy_, Nov 02 2019
%E a(4) from _Giovanni Resta_, Nov 04 2019
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