A146948 Semiprimes n such that n+1 and n+2 are squarefree.

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

Offset

1,1

Comments

Terms computed by Zak Seidov.

Except 4, all terms == 1 (mod 4). - Robert Israel, May 14 2020

Links

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

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

Adjacent sequences: A146945 A146946 A146947 * A146949 A146950 A146951

Keyword

nonn,less

Author

Giovanni Teofilatto, Nov 03 2008

Status

approved