A119705 Primes p such that the number of divisors of p+1 equals number of divisors of p+2.

13, 37, 43, 97, 103, 157, 229, 241, 331, 373, 433, 541, 547, 877, 907, 1021, 1129, 1201, 1373, 1381, 1433, 1489, 1543, 1597, 1613, 1621, 1741, 1831, 1951, 1987, 2017, 2053, 2161, 2377, 2503, 2539, 2557, 2633, 2677, 2713, 2857, 2953, 3061, 3067, 3109, 3169

Offset: 1

Author

Zak Seidov, Jul 29 2006

Keywords

• nonn

Comments

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

Examples

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

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

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

Programs

Mathematica

Select[Range[3200], PrimeQ[#] && DivisorSigma[0, # + 1] == DivisorSigma[0, # + 2] &] (* Amiram Eldar, Jan 26 2020 *)

PARI

isok(n) = isprime(n) && (numdiv(n+1) == numdiv(n+2)); \\ Michel Marcus, Oct 10 2013