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 A222563 Primes p such that the sum of divisors (excluding 1 and p - 1) of p - 1 and the sum of divisors (excluding 1 and p + 1) of p + 1 are both prime. 1
 5, 59, 83, 239, 281, 359, 443, 479, 521, 599, 761, 839, 1163, 1319, 1361, 1583, 1619, 1721, 1787, 1871, 1877, 2003, 2063, 2339, 2927, 2969, 3251, 3371, 3407, 3671, 3767, 3917, 4001, 4013, 4229, 4283, 4397, 4451, 4463, 4649, 4679, 5147, 5261, 6287, 6329, 6659, 6689 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Paolo P. Lava, Table of n, a(n) for n = 1..1000 EXAMPLE 83 is in the sequence because: it is prime, the sum of divisors (excluding 1 and 82) of 82 is 2 + 41 = 43, which is prime, and the sum of divisors (excluding 1 and 84) of 84 is 2 + 3 + 4 + 6 + 7 + 12 + 14 + 21 + 28 + 42 = 139, which is also prime. MATHEMATICA Select[Prime[Range[2, 900]], AllTrue[{Total[Most[Rest[Divisors[#-1]]]], Total[ Most[Rest[Divisors[#+1]]]]}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, May 29 2016 *) PROG (PARI) is(n)=isprime(n)&&isprime(sigma(n-1)-n)&&isprime(sigma(n+1)-n-2) \\ Charles R Greathouse IV, Feb 25 2013 CROSSREFS Cf. A048050, A085842. Sequence in context: A096476 A158694 A015994 * A141951 A243701 A179028 Adjacent sequences: A222560 A222561 A222562 * A222564 A222565 A222566 KEYWORD nonn AUTHOR Gerasimov Sergey, Feb 25 2013 EXTENSIONS Extended and a(4) and a(6) inserted by Charles R Greathouse IV, Feb 25 2013 STATUS approved

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Last modified September 22 18:47 EDT 2023. Contains 365531 sequences. (Running on oeis4.)