A069232 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

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

MATHEMATICA

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

PROG

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

CROSSREFS

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

Sequence in context: A226491 A062933 A348064 * A269232 A181920 A123012