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A067531 Numbers n such that n - number of divisors of n is a prime. 4
5, 6, 7, 13, 15, 16, 19, 21, 27, 31, 33, 35, 43, 51, 57, 61, 65, 73, 77, 87, 93, 103, 105, 109, 111, 135, 139, 141, 143, 151, 155, 161, 165, 177, 181, 183, 185, 189, 193, 199, 201, 203, 215, 229, 231, 237, 241, 245, 267, 271, 275, 283, 285, 287, 313, 321, 335 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Larger of the twin primes (A006512) is a term.

LINKS

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

EXAMPLE

51 is a term as d(51) = 4 and 51-4 = 47 is a prime.

MAPLE

with(numtheory): for n from 3 to 500 do if isprime(n-tau(n)) then printf(`%d, `, n) fi:od: # James A. Sellers, Feb 18 2002

MATHEMATICA

Select[Range[400], PrimeQ[#-DivisorSigma[0, #]]&] (* Harvey P. Dale, May 22 2013 *)

CROSSREFS

Cf. A000005 (number of divisors of n), A006512.

Sequence in context: A006991 A047574 A273929 * A031029 A134985 A111018

Adjacent sequences:  A067528 A067529 A067530 * A067532 A067533 A067534

KEYWORD

easy,nonn

AUTHOR

Amarnath Murthy, Feb 17 2002

EXTENSIONS

More terms from James A. Sellers, Feb 18 2002

STATUS

approved

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Last modified August 15 00:52 EDT 2020. Contains 336484 sequences. (Running on oeis4.)