OFFSET
1,2
COMMENTS
3, 7, 17, 41, 937 and 105943891 are primes.
EXAMPLE
a(12) = 1 + 2 + 4 + 10 + 24 + 46 + 100 + 225 + 525 + 1225 + 3136 + 7056 = 12354.
CROSSREFS
KEYWORD
nonn
AUTHOR
Jonathan Vos Post, May 16 2008
EXTENSIONS
a(4)=17 added and a(13)-a(25) from Akshay Bansal, Jul 08 2017
STATUS
approved