A119711 Primes p such that p+1, p+2 and p+3 have equal number of divisors.

229, 241, 373, 1831, 2053, 2503, 3109, 5861, 6053, 6151, 6871, 8293, 8821, 9161, 9829, 12049, 13591, 13781, 14293, 14887, 16087, 17737, 19141, 19333, 20389, 21493, 23333, 23509, 24151, 25771, 27109, 28807, 29269, 31337, 33413, 33941, 35509

Offset

1,1

Links

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

Example

229 is OK since 230, 231 and 232 all have 8 divisors: {1,2,5,10,23,46,115,230}, {1,3,7,11,21,33,77,231} and {1,2,4,8,29,58,116,232}.

Mathematica

Select[Prime@Range@5000, DivisorSigma[0, #+1]==DivisorSigma[0, #+2]==DivisorSigma[0, #+3]&]

Crossrefs

Cf. A008329, A049234.

Sequence in context: A086002 A061783 A140017 * A062589 A342368 A250235

Adjacent sequences: A119708 A119709 A119710 * A119712 A119713 A119714

Keyword

nonn

Author

Zak Seidov, Jul 29 2006

Status

approved