OFFSET
1,20
COMMENTS
Terms are also perfect squares.
Conjecture: a(n) = 0 for no n > 28. - Zhi-Wei Sun, Aug 26 2013
General conjecture: Let m be any nonnegative integer, and let a(m,n) be the n X n determinant with (i,j)-entry equal to 1 or 0 according as i^{2^m}+j^{2^m} is prime or not. Then a(m,n) is nonzero for large n. (It can be proved that (-1)^(n*(n-1)/2)*a(m,n) is always a square, see the comments in A228591.) - Zhi-Wei Sun, Aug 26-27 2013
MATHEMATICA
a[n_]:=a[n]=Det[Table[If[PrimeQ[i^2+j^2]==True, 1, 0], {i, 1, n}, {j, 1, n}]]; Table[a[n], {n, 1, 30}] (* Zhi-Wei Sun, Aug 26 2013 *)
Table[Det[Table[If[PrimeQ[a^2+b^2], 1, 0], {a, n}, {b, n}]], {n, 60}] (* Harvey P. Dale, May 31 2019 *)
PROG
(PARI) for(n=1, 60, print1(((matdet(matrix(n, n, i, j, isprime(i^2+j^2))))), ", "))
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Benoit Cloitre, Jun 02 2002
STATUS
approved