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 A333364 Indices of primes p whose order of primeness A078442(p) is prime. 2
 2, 3, 7, 11, 13, 17, 19, 23, 29, 37, 41, 43, 47, 53, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are prime. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 N. Fernandez, An order of primeness, F(p) N. Fernandez, An order of primeness [cached copy, included with permission of the author] FORMULA { p in primes : A049076(p) is prime }. a(n) = pi(A333353(n)), with pi = A000720. EXAMPLE 11 is a term: prime(11) = 31 -> 11 -> 5 -> 3 -> 2 -> 1, five (a prime number of) steps "->" = pi = A000720. MAPLE b:= proc(n) option remember; `if`(isprime(n), 1+b(numtheory[pi](n)), 0) end: a:= proc(n) option remember; local p; p:= `if`(n=1, 1, a(n-1)); do p:= nextprime(p); if isprime(b(p)+1) then break fi od; p end: seq(a(n), n=1..62); MATHEMATICA b[n_] := b[n] = If[PrimeQ[n], 1 + b[PrimePi[n]], 0]; a[n_] := a[n] = Module[{p}, p = If[n == 1, 1, a[n - 1]]; While[True, p = NextPrime[p]; If[PrimeQ[b[p] + 1], Break[]]]; p]; Table[a[n], {n, 1, 62}] (* Jean-François Alcover, Sep 14 2022, after Alois P. Heinz *) CROSSREFS Cf. A000040, A000720, A049076, A333353. Sequence in context: A020634 A173555 A086339 * A332787 A181173 A216277 Adjacent sequences: A333361 A333362 A333363 * A333365 A333366 A333367 KEYWORD nonn AUTHOR Alois P. Heinz, Mar 16 2020 STATUS approved

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Last modified November 29 08:15 EST 2023. Contains 367429 sequences. (Running on oeis4.)