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Primes p such that the number of divisors of p+1 equals number of divisors of p+2.
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%I #15 Jan 26 2020 11:02:44

%S 13,37,43,97,103,157,229,241,331,373,433,541,547,877,907,1021,1129,

%T 1201,1373,1381,1433,1489,1543,1597,1613,1621,1741,1831,1951,1987,

%U 2017,2053,2161,2377,2503,2539,2557,2633,2677,2713,2857,2953,3061,3067,3109,3169

%N Primes p such that the number of divisors of p+1 equals number of divisors of p+2.

%C Primes p such that A008329(p) = A049234(p).

%H Amiram Eldar, <a href="/A119705/b119705.txt">Table of n, a(n) for n = 1..10000</a>

%e 13 is a term because 14 and 15 each have 4 divisors: {1, 2, 7, 14} and {1, 3, 5, 15}.

%t Select[Range[3200], PrimeQ[#] && DivisorSigma[0, # + 1] == DivisorSigma[0, # + 2] &] (* _Amiram Eldar_, Jan 26 2020 *)

%o (PARI) isok(n) = isprime(n) && (numdiv(n+1) == numdiv(n+2)); \\ _Michel Marcus_, Oct 10 2013

%Y Cf. A008329, A049234, A119711, A119728, A119730, A119740.

%K nonn

%O 1,1

%A _Zak Seidov_, Jul 29 2006