OFFSET
1,2
COMMENTS
Sum of 7 consecutive squares starting with n^2 is equal to 7*(13 + 6*n + n^2) and mean is (13 + 6*n + n^2)=(n+3)^2+4. Hence a(n)=A007591(n+1)-3
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
(0^2+...+6^2)/7=13 prime, (2^2+...+8^2)/7=29 prime, (4^2+...+10^2)/7=53 prime.
MATHEMATICA
Select[Range[0, 400], PrimeQ[Mean[Range[#, #+6]^2]]&] (* Harvey P. Dale, Apr 23 2011 *)
PROG
(PARI) is(n)=isprime(n^2+6*n+13) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Zak Seidov, Apr 14 2007
STATUS
approved