

A239323


Semiprimes of the form (2^n + 1)*(2^n  n + 1).


0




OFFSET

1,1


COMMENTS

Generated by n: 0, 1, 2, 4, 16, ...
The positions of a(n) in A001358: 1, 2, 6, 75, ...


LINKS

Table of n, a(n) for n=1..5.


EXAMPLE

4 is in this sequence because (2^0 + 1)*(2^0  0 + 1) = 2*2 = 4 is semiprime for n = 0,
6 is in this sequence because (2^1 + 1)*(2^1  1 + 1) = 3*2 = 6 is semiprime for n = 1,
15 is in this sequence because (2^2 + 1)*(2^2  2 + 1) = 5*3 = 15 is semiprime for n = 2.


PROG

(MAGMA) k := 1;
for n in [1..10000] do
if IsPrime(k*2^n + 1) and IsPrime(k*2^n  n + 1) then
(k*2^n + 1)*(k*2^n  n + 1);
end if;
end for;


CROSSREFS

Cf. A019434, A100361, A100362.
Sequence in context: A305580 A191311 A086714 * A009463 A066260 A248591
Adjacent sequences: A239320 A239321 A239322 * A239324 A239325 A239326


KEYWORD

nonn


AUTHOR

JuriStepan Gerasimov, Mar 15 2014


STATUS

approved



