A176570 a(n)=n-th semiprime if n-th semiprime odd and n-th semiprime/2 if n-th semiprime even.

2, 3, 9, 5, 7, 15, 21, 11, 25, 13, 33, 17, 35, 19, 39, 23, 49, 51, 55, 57, 29, 31, 65, 69, 37, 77, 41, 85, 43, 87, 91, 93, 47, 95, 53, 111, 115, 59, 119, 121, 61, 123, 129, 133, 67, 141, 71, 143, 145, 73, 155, 79, 159, 161, 83, 169, 177, 89, 183, 185, 187, 97, 201, 101, 203

Offset

1,1

Links

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

Mathematica

If[EvenQ[#], #/2, #]&/@Select[Range[300], PrimeOmega[#]==2&] (* Harvey P. Dale, Nov 01 2019 *)

Crossrefs

Cf. A001358.

Sequence in context: A065631 A222244 A325645 * A269559 A083173 A120725

Adjacent sequences: A176567 A176568 A176569 * A176571 A176572 A176573

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 20 2010

Extensions

Entries checked by R. J. Mathar, Apr 27 2010

Status

approved