OFFSET
2,1
EXAMPLE
a(1) = 1*2 + 2*5 = 12 = 4*3 = 4* prime(2). r = 1 and s = 2 both r and s are positive integers.
a(9) = 1*23 + 3*31 =116 =4*29 = 4*prime(10).
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy and Jason Earls, Jul 15 2003
EXTENSIONS
Corrected and extended by David Wasserman, Feb 15 2005
STATUS
approved