%I #11 Mar 31 2012 13:21:02

%S 2,3,5,7,11,19,23

%N Primes which cannot be written as sum of squares>1.

%C Equivalently, prime numbers which cannot be written as sum of squares of primes (see A078137 for the proof). - _Hieronymus Fischer_, Nov 11 2007

%C Equivalently, prime numbers which cannot be written as sum of squares of 2 and 3 (see A078137 for the proof). - _Hieronymus Fischer_, Nov 11 2007

%C The sequence is finite, since numbers > 23 can be written as sums of squares >1 (see A078135). - _Hieronymus Fischer_, Nov 11 2007

%C Explicit representation as sum of squares of primes, or rather of squares of 2 and 3, for numbers m>23: we have m=c*2^2+d*3^2, where c:=((floor(m/4) - 2*(m mod 4))>=0, d:=m mod 4. For that, the finiteness of the sequence is proved. - _Hieronymus Fischer_, Nov 11 2007

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SquareNumber.html">Square Number</a>.

%H <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>

%Y Cf. A000290, A078134, A078138, A000040, A078133.

%Y Cf. A078135, A090677, A078137, A134754, A134755.

%K nonn,fini,full

%O 1,1

%A _Reinhard Zumkeller_, Nov 19 2002