

A136196


Numbers n such that n and n+2 are consecutive semiprimes.


7



4, 49, 55, 91, 119, 143, 159, 183, 185, 203, 215, 219, 235, 247, 265, 287, 289, 299, 303, 319, 321, 327, 339, 391, 411, 413, 415, 451, 469, 471, 515, 517, 527, 533, 535, 543, 551, 579, 581, 589, 667, 669, 679, 685, 687, 695, 721, 753, 779, 789, 791, 813, 815
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OFFSET

1,1


LINKS



EXAMPLE

4 and 6 are 1st and 2nd semiprimes,
49 and 51 are 17th and 18th semiprimes,
55 and 57 are 19th and 20th semiprimes.


MATHEMATICA

Position[Partition[PrimeOmega[Range[900]], 3, 1], _?(#[[1]]==#[[3]]==2 && #[[2]]!=2&), 1, Heads>False]//Flatten (* Harvey P. Dale, Oct 15 2021 *)


PROG

(PARI) isok(n) = (bigomega(n) == 2) && (bigomega(n+2) == 2) && (bigomega(n+1) != 2); \\ Michel Marcus, Oct 13 2013


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



