A144482 Semiprimes that are a product of Mersenne primes.

9, 21, 49, 93, 217, 381, 889, 961, 3937, 16129, 24573, 57337, 253921, 393213, 917497, 1040257, 1572861, 3670009, 4063201, 16252897, 16646017, 66584449, 67092481, 1073602561, 4294434817, 6442450941, 15032385529, 17179607041

Offset

1,1

Comments

As the product of any two primes is semiprime by definition, this is also the list of composite numbers n=x*y where both x and y are Mersenne primes. - Christian N. K. Anderson, Mar 25 2013

Links

Christian N. K. Anderson, Table of n, a(n) for n = 1..75

Mathematica

Take[Times@@@Tuples[2^# -1&/@MersennePrimeExponent[Range[10]], 2]//Union, 30] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 30 2020 *)

Prog

(PARI)
isA000668(n) = (isprime(n)&&!bitand(n, 1+n));
isA144482(n) = ((2==bigomega(n))&&isA000668(vecmin(factor(n)[, 1]))&&isA000668(vecmax(factor(n)[, 1]))); \\ Antti Karttunen, Jun 28 2020

Crossrefs

Cf. A000668, A001358, A144856, A333788.

Subsequence of A335882.

Sequence in context: A256530 A363634 A118130 * A251212 A176896 A347502

Adjacent sequences: A144479 A144480 A144481 * A144483 A144484 A144485

Keyword

nonn

Author

G. L. Honaker, Jr., Oct 12 2008

Status

approved