OFFSET
1,2
COMMENTS
a(n) = 3 iff n is prime.
FORMULA
Row sums of triangle A156837.
EXAMPLE
a(4) = 7 since row 4 of triangle A156837 = (3, 3, 0, 1).
MAPLE
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Gary W. Adamson & Mats Granvik, Feb 16 2009
EXTENSIONS
Extended beyond a(14) by R. J. Mathar, Mar 03 2013
STATUS
approved