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A264046
Numbers k such that k and k+6 are consecutive semiprimes.
2
15, 123, 365, 371, 505, 545, 573, 591, 649, 707, 807, 843, 943, 1067, 1159, 1247, 1357, 1405, 1529, 1555, 1633, 1739, 1745, 1829, 1843, 1897, 1909, 1985, 2149, 2159, 2209, 2285, 2329, 2353, 2363, 2407, 2413, 2463, 2501, 2643, 2773, 2779
OFFSET
1,1
COMMENTS
Note that a(1) = 15 = A131109(k=6).
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
15 = A001358(6) and 21 = A001358(7).
MATHEMATICA
Select[Partition[Select[Range[3000], PrimeOmega[#]==2&], 2, 1], #[[2]]-#[[1]]==6&][[;; , 1]] (* Harvey P. Dale, Dec 24 2023 *)
PROG
(PARI) is(n)=if(bigomega(n)!=2 || bigomega(n+6)!=2, return(0)); for(i=1, 5, if(bigomega(n+i)==2, return(0))); 1 \\ Charles R Greathouse IV, Nov 02 2015
KEYWORD
nonn
AUTHOR
Zak Seidov, Nov 02 2015
STATUS
approved