1,11

For odd n, n^2 is odd so the two primes must be opposite in parity. Lesser prime must be 2 and greater prime must be n^2-2. Thus for odd n, n^2 is the sum of two primes iff n^2-2 is prime. (Chandler)

Table of n, a(n) for n=1..81.

a(n) = n^2 - A106545(n).

a(10)=0 because 10^2=100=97+3 (sum of two primes)

a(11)=11^2=121, which is impossible to obtain summing two primes.

Cf. A106545-A106548, A106562-A106564, A106571, A106573-A106575, A106577.

Sequence in context: A045509 A033187 A106547 * A079842 A014756 A014748

Adjacent sequences: A106541 A106542 A106543 * A106545 A106546 A106547

easy,nonn

Alexandre Wajnberg, May 08 2005

Extended by Ray Chandler, May 12 2005

approved