OFFSET
0,4
COMMENTS
36*k^2 + 12*k + 5 = (6*k+1)^2 + 4, which is four more than a square. Except for a(0), a(n) is never a multiple of 5.
EXAMPLE
a(3)=2 since 36*2^2 + 12*2 + 5 = 173 which is prime (as well as being four more than a square).
CROSSREFS
KEYWORD
sign
AUTHOR
Henry Bottomley, Jul 07 2000
STATUS
approved