OFFSET
1,1
COMMENTS
The n-th Woodall number is Wn = n*2^n - 1.
If Wn is semiprime, it is in the sequence.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..47 (terms 1..26 from K. D. Bajpai)
FORMULA
EXAMPLE
a(1) = 159 = (5*2^5 - 1) is 5th Woodall number and 159 = 3*53 which is semiprime.
a(2) = 895 = (7*2^7 - 1) is 7th Woodall number and 895 = 5*179 which is semiprime.
MAPLE
MATHEMATICA
Select[Table[n*2^n-1, {n, 100}], PrimeOmega[#]==2&] (* Harvey P. Dale, Jan 03 2019 *)
PROG
(PARI) for(n=1, 1000, if(bigomega(n*2^n-1)==2, print1(n*2^n-1, ", "))) \\ Colin Barker, May 07 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
K. D. Bajpai, May 04 2014
STATUS
approved