A092126 Numbers n such that n, n+2, n+4, n+6 are semiprimes.

213, 215, 299, 411, 1133, 1135, 1343, 1345, 1383, 1385, 1387, 1685, 1793, 1835, 1837, 1891, 1937, 1939, 1957, 2045, 2315, 2317, 2513, 2567, 2807, 2809, 2929, 3091, 3093, 3095, 3097, 3147, 3149, 3647, 3957, 3977, 3979, 4115, 4313, 4315, 4411, 4529, 4531

Offset

1,1

Comments

Semiprimes in arithmetic progression. All terms are odd, see also A056809.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

PrimeFactorExponentsAdded[n_] := Plus @@ Flatten[Table[ #[[2]], {1}] & /@ FactorInteger[n]]; Select[ Range[ 4626], PrimeFactorExponentsAdded[ # ] == PrimeFactorExponentsAdded[ # + 2] == PrimeFactorExponentsAdded[ # + 4] == PrimeFactorExponentsAdded[ # + 6] == 2 &] (* Robert G. Wilson v, Feb 24 2004 *)
Transpose[SequencePosition[Table[If[PrimeOmega[n]==2, 1, 0], {n, 5000}], {1, _, 1, _, 1, _, 1}]][[1]] (* The program uses the SequencePosition function from Mathematica version 10 *) (* Harvey P. Dale, Feb 10 2016 *)

Crossrefs

Cf. A056809, A070552, A092125, A092127, A092128, A092129.

Sequence in context: A197106 A138568 A201104 * A252032 A252025 A238019

Adjacent sequences: A092123 A092124 A092125 * A092127 A092128 A092129

Keyword

easy,nonn

Author

Zak Seidov, Feb 22 2004

Status

approved