A283597 Numbers n such that both 6n+1 and 6n+7 are semiprimes.

8, 14, 19, 41, 42, 43, 48, 49, 59, 74, 84, 85, 88, 92, 93, 97, 108, 113, 116, 132, 139, 144, 148, 149, 157, 158, 159, 162, 163, 189, 190, 193, 198, 209, 210, 211, 222, 223, 224, 225, 226, 227, 231, 234, 235, 250, 251, 259, 264, 272, 280, 285, 306, 307, 315, 316, 317, 318, 319, 320, 323, 326, 327, 340, 345, 349, 358, 361, 368, 376, 386, 387, 388

Offset

1,1

Comments

Both n and n+1 are terms in A112775.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

filter:= n -> numtheory:-bigomega(6*n+1) = 2 and numtheory:-bigomega(6*n+7) = 2:
select(filter, [$1..1000]); # Robert Israel, Dec 23 2024

Mathematica

po[x_]=PrimeOmega[x]; Select[Range[500], po[6# + 1] == po[6# + 7] == 2 &]

Prog

(PARI) for(n=1, 388, if(bigomega(6*n + 1) == 2 && bigomega(6*n + 7) == 2, print1(n, ", "))) \\ Indranil Ghosh, Mar 15 2017

Crossrefs

Cf. A112771 (6n+1 semiprimes), A112775 (6n+1 is semiprime), A001358 (semiprimes).

Sequence in context: A096229 A231718 A212020 * A112277 A078754 A068638

Adjacent sequences: A283594 A283595 A283596 * A283598 A283599 A283600

Keyword

nonn

Author

Zak Seidov, Mar 14 2017

Status

approved