A079260 - OEIS

A079260

Characteristic function of primes of form 4n+1 (1 if n is prime of form 4n+1, 0 otherwise).

0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0

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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(A002144(n)) = 1; a(A137409(n)) = 0. [From Reinhard Zumkeller, Oct 11 2008]

a(n) * A151763(n) = a(n).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Index entries for characteristic functions

MATHEMATICA

Table[If[PrimeQ[n]&&IntegerQ[(n-1)/4], 1, 0], {n, 120}] (* Harvey P. Dale, Jul 14 2015 *)