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A336380 Primes p(n) such that gcd(n, prime(n-1)+prime(n+1)) = 1. 4
3, 5, 17, 41, 59, 67, 83, 103, 109, 127, 157, 179, 191, 197, 211, 227, 241, 257, 277, 283, 307, 313, 331, 347, 353, 367, 389, 401, 419, 431, 439, 461, 467, 487, 499, 509, 547, 563, 587, 599, 607, 617, 643, 653, 661, 691, 709, 739, 751, 761, 773, 797, 811 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..54.

EXAMPLE

In the following table, p(n) = A000040(n) = prime(n).

  n    p(n)   p(n-1)+p(n+1)   gcd

  2     3          7           1

  3     5         10           1

  4     7         16           4

  5    11         20           5

  6    13         28           2

2 and 3 are in A336378; 4 and 5 are in A336379; 3 and 5 are in A336380; 7 and 11 are in A336381.

MATHEMATICA

p[n_] := Prime[n];

u = Select[Range[2, 200], GCD[#, p[# - 1] + p[# + 1]] == 1 &]  (* A336378 *)

v = Select[Range[2, 200], GCD[#, p[# - 1] + p[# + 1]] > 1 &]   (* A336379 *)

Prime[u]  (* A336380 *)

Prime[v]  (* A336381 *)

CROSSREFS

Cf. A000040, A336366, A336378, A336379, A336381.

Sequence in context: A148522 A308588 A141160 * A113275 A280080 A001572

Adjacent sequences:  A336377 A336378 A336379 * A336381 A336382 A336383

KEYWORD

nonn

AUTHOR

Clark Kimberling, Oct 25 2020

STATUS

approved

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Last modified June 14 12:04 EDT 2021. Contains 345025 sequences. (Running on oeis4.)