A069232 Numbers n such that there are exactly 2 primes p satisfying the inequality n < p < n + tau(n)^2 where tau(n) = A000005(n).

2, 25, 85, 118, 119, 133, 141, 194, 209, 213, 235, 247, 253, 323, 326, 327, 329, 355, 362, 381, 391, 393, 398, 411, 413, 415, 422, 445, 466, 473, 481, 482, 493, 501, 502, 511, 514, 515, 517, 519, 533, 535, 537, 538, 542, 543, 545, 551, 553, 573, 579, 581, 583

Offset: 1

Author

Benoit Cloitre, Apr 13 2002

Keywords

• easy
• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000005, A049591, A069230, A069231, A069233.

Programs

Mathematica

Select[Range[900],Length[Select[Range[#+1,#+DivisorSigma[0,#]^2-1],PrimeQ]] == 2&] (* Harvey P. Dale, Sep 20 2020 *)

PARI

isok(n) = #select(x->isprime(x), vector(numdiv(n)^2-1, k, k+n)) == 2; \\ Michel Marcus, Jun 18 2017

Extensions

Missing term 2 added by Michel Marcus, Jun 18 2017