

A089268


Odd semiprimes m such that m2 is composite.


3



35, 51, 57, 65, 77, 87, 93, 95, 119, 121, 123, 143, 145, 155, 161, 177, 185, 187, 203, 205, 209, 215, 217, 219, 221, 237, 247, 249, 267, 287, 289, 291, 299, 301, 303, 305, 321, 323, 327, 329, 335, 341, 365, 371, 377, 393, 395, 407, 413, 415, 417, 427, 437
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

A087942(a(n)) = 0.
Assuming Goldbach's conjecture that every even number greater than 2 is the sum of two primes, these are the numbers that are the product of two primes but not the sum of two primes.  Michael B. Porter, Feb 08 2013


LINKS

Table of n, a(n) for n=1..53.


MATHEMATICA

Take[Select[Union[Flatten[Table[Prime[i] Prime[j], {i, 2, 25}, {j, 2, 25}]]], Not[PrimeQ[#  2]] &], 50] (* Alonso del Arte, Feb 08 2013 *)


CROSSREFS

Cf. A062721, A046315, A001358.
Sequence in context: A249819 A186319 A248659 * A214469 A306117 A039418
Adjacent sequences: A089265 A089266 A089267 * A089269 A089270 A089271


KEYWORD

nonn


AUTHOR

Reinhard Zumkeller, Oct 28 2003


STATUS

approved



