OFFSET
1,3
COMMENTS
This relates primes between n^2 and (n+1)^2 to primes between (n+1)^2 and (n+2)^2. It appears that the number of symmetric primes is zero for only n=0,32,41.
LINKS
T. D. Noe, Table of n, a(n) for n=1..10000
EXAMPLE
a(5) = 1 because in the range 25 to 49, the primes 29 and 41 are the only primes symmetric about the number 35.
MATHEMATICA
maxN=100; lst={}; For[n=1, n<maxN, n=n+1, mid=n^2+2n; cnt=0; If[EvenQ[mid], k=1, k=2]; While[k<2n, If[PrimeQ[mid-k]&&PrimeQ[mid+k], cnt++; ]; k=k+2]; AppendTo[lst, cnt] ]; lst
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
T. D. Noe, Apr 09 2002
STATUS
approved