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 A329026 Numbers k such that k = Product (p_j^e_j) = concatenation (pi(p_j)), where pi = A000720. 1
 12, 14, 2127, 1232495490 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers k such that k equals concatenation of indices of distinct prime factors of k, in increasing order. Fixed points of A329025. a(5) > 2.4*10^11, if it exists. - Giovanni Resta, Nov 05 2019 LINKS EXAMPLE 2127 is a term because 2127 = 3 * 709 = prime(2) * prime(127) = concat(2, 127). MATHEMATICA a[n_] := FromDigits[Flatten@IntegerDigits@(PrimePi[#[[1]]] & /@ FactorInteger[n])]; Select[Range[2200], a[#] == # &] CROSSREFS Cf. A000720, A329025. Sequence in context: A318298 A139310 A221819 * A307535 A180575 A115402 Adjacent sequences:  A329023 A329024 A329025 * A329027 A329028 A329029 KEYWORD nonn,base,more AUTHOR Ilya Gutkovskiy, Nov 02 2019 EXTENSIONS a(4) from Giovanni Resta, Nov 04 2019 STATUS approved

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Last modified April 6 08:53 EDT 2020. Contains 333268 sequences. (Running on oeis4.)