login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A092126 Numbers n such that n, n+2, n+4, n+6 are semiprimes. 10
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified March 24 22:17 EDT 2017. Contains 284035 sequences.