OFFSET
1,1
COMMENTS
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
EXAMPLE
a(4) = hexagonal(2) + hexagonal(3) + hexagonal(5) + hexagonal(7) = 6 + 15 + 45 + 91 = 157 is prime.
a(12) = 6 + 15 + 45 + 91 + 231 + 325 + 561 + 703 + 1035 + 1653 + 1891 + 2701 = 9257 is prime.
a(26) = 150833 is prime.
MATHEMATICA
Accumulate[Table[n(2n-1), {n, Prime[Range[50]]}]] (* Harvey P. Dale, Jan 30 2014 *)
CROSSREFS
KEYWORD
easy,nonn,less
AUTHOR
Jonathan Vos Post, Apr 05 2006
STATUS
approved