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 A266233 Primes representable as f(f(f(...f(p)...))) where p is a prime and f(x) = x*2 + 1. 4
 5, 7, 11, 23, 31, 47, 59, 71, 79, 83, 107, 127, 151, 167, 179, 191, 223, 227, 239, 263, 271, 347, 359, 383, 431, 439, 467, 479, 503, 563, 587, 599, 607, 631, 719, 727, 839, 863, 887, 911, 919, 967, 983, 991, 1019, 1031, 1087, 1103, 1151, 1187, 1231, 1279, 1283 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A005385 is a subsequence: f(x) is applied just once. LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE a(5) = f(f(7)) = (7*2 + 1)*2 + 1 = 31. a(48) = f(f(f(137))) = ((137*2 + 1)*2 + 1)*2 + 1 = 1103. MAPLE N:= 10^4: # to get all terms <= N Primes:= select(isprime, {2, seq(i, i=3..N, 2)}): f:= x -> 2*x+1: S:= {}: R:= Primes: for k from 1 while nops(R) > 0 do R:= select(`<=`, map(f, R), N); S:= S union (R intersect Primes); od: sort(convert(S, list)); # Robert Israel, Jun 29 2016 MATHEMATICA Take[Select[Union@ Flatten[Table[Nest[2 # + 1 &, Prime@ n, #], {n, 120}] & /@ Range@ 120], PrimeQ], 53] (* Michael De Vlieger, Jan 06 2016 *) PROG (Python) from sympy import isprime a=[] TOP=10000 for p in range(TOP): if isprime(p): while p

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Last modified September 27 04:57 EDT 2023. Contains 365674 sequences. (Running on oeis4.)