

A289250


Primes p such that p + 4 is a semiprime.


2



2, 5, 11, 17, 29, 31, 47, 53, 61, 73, 83, 89, 107, 137, 139, 151, 157, 173, 179, 181, 197, 199, 211, 233, 263, 283, 317, 331, 337, 367, 373, 389, 409, 433, 443, 449, 467, 523, 541, 547, 569, 577, 587, 593, 607, 619, 631, 677, 683, 691, 709, 719, 727, 733, 751, 787, 809, 811, 827
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OFFSET

1,1


COMMENTS

Except for case p=5, p+4 is never a perfect square.
For p = {2, 11, 31, 73, 139, 433, 1759, 2017} p+4 is a product of two consecutive primes.


LINKS



EXAMPLE

2+4=6=2*3, 5+4=9=3*3, 11+4=15=3*5 (all semiprimes).


MATHEMATICA



PROG

(PARI) issemi(n)=bigomega(n)==2


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



