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A089268 Odd semiprimes m such that m-2 is composite. 4
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
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 *)
PROG
(PARI) isok(m) = (m%2) && (bigomega(m)==2) && !isprime(m-2); \\ Michel Marcus, Oct 19 2021
CROSSREFS
Sequence in context: A249819 A186319 A248659 * A214469 A306117 A039418
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 28 2003
STATUS
approved

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Last modified July 21 13:28 EDT 2024. Contains 374474 sequences. (Running on oeis4.)