A175509 a(n) = ((2*n)-th semiprime) minus 2*(n-th semiprime).

-2, -2, -3, 2, -2, 4, -4, 2, 1, 5, -4, 1, 7, 9, 9, 1, -3, 9, 8, 7, 7, 9, 11, 5, -2, 4, -3, -1, 6, 11, 12, 16, 17, 19, 2, -5, -11, -10, -1, 7, 10, 16, 9, 12, 21, 13, 15, 16, 15, 22, 11, 10, 11, 13, 9, 17, 7, 9, 11, 12, 17, 6, -4, 3, 7, 7, 15, 27, 21, 25, 28, 35, 37, 43, 43, 41, 31, 31, 20

Offset

1,1

Links

Table of n, a(n) for n=1..79.

Formula

a(n) = A099981(n) - A075818(n).

Example

a(1) = -2 because ((2*1)-th semiprime) - 2*(1st semiprime) = 6 - 2*4 = -2.

Crossrefs

Cf. A066066.

Sequence in context: A086454 A339492 A069360 * A213023 A068050 A210967

Adjacent sequences: A175506 A175507 A175508 * A175510 A175511 A175512

Keyword

sign

Author

Juri-Stepan Gerasimov, Jun 02 2010

Extensions

Entries checked by R. J. Mathar, Aug 12 2010

Status

approved