OFFSET
1,1
COMMENTS
Let M(n) denote the n X n matrix m(i,j)=0 if n divides ij-1, m(i,j) = 1 otherwise then det(M(n))=-1 if and only if n =2 or if n is prime ==1 (mod 4).
a(n) * A151763(n) = a(n).
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
MATHEMATICA
Table[If[PrimeQ[n]&&IntegerQ[(n-1)/4], 1, 0], {n, 120}] (* Harvey P. Dale, Jul 14 2015 *)
PROG
(PARI) { a(n)=if(n%4==1, isprime(n)) }; vector(100, n, a(n))
(Haskell)
a079260 n = fromEnum $ n `mod` 4 == 1 && a010051 n == 1
-- Reinhard Zumkeller, Oct 06 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 04 2003
STATUS
approved