OFFSET
1,1
EXAMPLE
a(1) = semiprime(1)*(semiprime(1)+1)/2 = 4*5/2 = 10.
a(2) = semiprime(2)*(semiprime(2)+1)/2 = 6*7/2 = 21.
a(3) = semiprime(3)*(semiprime(3)+1)/2 = 9*10/2 = 45.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, Oct 26 2006
EXTENSIONS
a(41)-a(46) from Giovanni Resta, Jun 13 2016
STATUS
approved