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 A317851 Primes p such that A090086(p+1) < p. 1
 31, 43, 61, 67, 73, 79, 97, 103, 107, 113, 127, 131, 137, 151, 163, 167, 173, 181, 191, 193, 197, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Theorem: if n-1 is composite, then A090086(n) < n. The inverse theorem is false iff n = p+1 for primes p in this sequence. Conjecture: the sequence contains all sufficiently large primes. Probably all primes except 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 37, 41, 47, 53, 59, 71, 83, 89, 101, 109, 139, 149, 157, 179, 199, 307, 461, and 571. LINKS EXAMPLE The prime 31 is a term, since A090086(31+1) = 25 < 31. PROG (PARI) b(n) = {forcomposite(k=2, , if (Mod(n, k)^(k-1) == 1, return (k)); ); } isok(p) = isprime(p) && (b(p+1) < p); \\ Michel Marcus, Aug 09 2018 CROSSREFS Cf. A000040, A090086. Sequence in context: A089713 A281246 A067467 * A304239 A069455 A211549 Adjacent sequences:  A317848 A317849 A317850 * A317852 A317853 A317854 KEYWORD nonn AUTHOR Thomas Ordowski, Aug 09 2018 EXTENSIONS Corrected and extended by Michel Marcus, Aug 09 2018 STATUS approved

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Last modified June 21 04:10 EDT 2021. Contains 345354 sequences. (Running on oeis4.)