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 A237687 Primes p with pi(p), pi(pi(p)) and pi(p^2) all prime, where pi(.) is given by A000720. 2
 59, 127, 709, 1153, 1787, 9319, 13709, 19577, 32797, 35023, 39239, 40819, 53353, 62921, 75269, 90023, 161159, 191551, 218233, 228451, 235891, 238339, 239087, 272999, 289213, 291619, 339601, 439357, 500741, 513683 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This is a subsequence of A237659. Conjecture: The sequence has infinitely many terms. LINKS Chai Wah Wu, Table of n, a(n) for n = 1..1000 (n = 1..150 from Zhi-Wei Sun) EXAMPLE a(1) = 59 with 59, pi(59) = 17, pi(pi(59)) = pi(17) = 7 and pi(59^2) = 487 all prime. MATHEMATICA p[m_]:=PrimeQ[PrimePi[m^2]] n=0; Do[If[p[Prime[Prime[Prime[k]]]], n=n+1; Print[n, " ", Prime[Prime[Prime[k]]]]], {k, 1, 1000}] CROSSREFS Cf. A000040, A000290, A000720, A006450, A038107, A038580, A237656, A237657, A237658, A237659. Sequence in context: A044627 A050230 A138633 * A098032 A139994 A107157 Adjacent sequences: A237684 A237685 A237686 * A237688 A237689 A237690 KEYWORD nonn AUTHOR Zhi-Wei Sun, Feb 11 2014 STATUS approved

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Last modified September 11 05:49 EDT 2024. Contains 375814 sequences. (Running on oeis4.)