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 A280720 For p = prime(n), number of iterations of the function f(x) = 5x + 2 that leave p prime. 5
 0, 1, 0, 1, 0, 2, 0, 3, 0, 0, 2, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 2, 0, 0, 2, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 2, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 2, 0, 0, 0, 4, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS Records are a(1) = 0 [p = 2], a(2) = 1 [p = 3], a(6) = 2 [p = 13], a(8) = 3 [p = 19], a(74) = 4 [p = 373], a(12656) = 6 [p = 135859], a(1165346) = 7 [p = 18235423], a(1659004) = 8 [p = 26588257], a(5386789) = 9 [p = 93112729], .... - Charles R Greathouse IV, Jan 12 2017 LINKS John Cerkan, Table of n, a(n) for n = 1..10001 MATHEMATICA Table[Length@ NestWhileList[5 # + 2 &, Prime@ n, PrimeQ] - 2, {n, 120}] (* Michael De Vlieger, Jan 09 2017 *) PROG (PARI) a016873(n) = 5*n+2 a(n) = my(p=prime(n), i=0); while(1, if(!ispseudoprime(a016873(p)), return(i), p=a016873(p); i++)) CROSSREFS Cf. A016873, A023217, A023252, A023283, A023313, A023341, A084958, A249573. Sequence in context: A085246 A268726 A035182 * A245964 A141700 A345228 Adjacent sequences: A280717 A280718 A280719 * A280721 A280722 A280723 KEYWORD nonn AUTHOR Felix Fröhlich, Jan 07 2017 STATUS approved

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Last modified March 1 16:12 EST 2024. Contains 370442 sequences. (Running on oeis4.)