login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A146948 Semiprimes n such that n+1 and n+2 are squarefree. 1
4, 9, 21, 33, 57, 65, 69, 77, 85, 93, 121, 129, 141, 177, 185, 201, 209, 213, 217, 221, 237, 253, 265, 289, 301, 309, 321, 329, 365, 381, 393, 417, 437, 445, 453, 469, 481, 497, 501, 517, 533, 545, 553, 581, 589, 597, 633, 669, 681, 689, 697, 713, 717, 753 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Terms computed by Zak Seidov.
Except 4, all terms == 1 (mod 4). - Robert Israel, May 14 2020
LINKS
MAPLE
filter:= n -> numtheory:-bigomega(n)=2 and numtheory:-issqrfree(n+1) and numtheory:-issqrfree(n+2):
select(filter, [4, seq(i, i=5..1000, 4)]); # Robert Israel, May 14 2020
MATHEMATICA
Select[Range[800], PrimeOmega[#]==2&&And@@SquareFreeQ/@(#+{1, 2})&] (* Harvey P. Dale, Oct 30 2013 *)
CROSSREFS
Sequence in context: A290434 A230834 A120535 * A033944 A287143 A238641
KEYWORD
nonn,less
AUTHOR
Giovanni Teofilatto, Nov 03 2008
STATUS
approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 29 20:48 EST 2024. Contains 370428 sequences. (Running on oeis4.)