A120293 - OEIS

A120293

Absolute value of numerator of determinant of n X n matrix with M(i,j) = (i+1)/(i+2) if i=j otherwise 1.

%I #5 Sep 08 2012 13:12:51

%S 2,1,11,17,1,1,41,17,31,37,29,101,29,1,149,167,31,103,227,83,1,37,107,

%T 347,1,67,431,461,41,131,557,197,313,331,233,67,97,1,857,1,157,1,1031,

%U 359,281,293,1,1,661,229,1427,1481,1,199,97,569,883,83,1,1949,503,173

%N Absolute value of numerator of determinant of n X n matrix with M(i,j) = (i+1)/(i+2) if i=j otherwise 1.

%C Some a(n) are equal to 1 (n=2,5,6,14,21,25,38,40,42,47,48,53,59,69,70..). All other a(n) are primes that belong to A038907 (33 is a square mod p).

%H Vincenzo Librandi, <a href="/A120293/b120293.txt">Table of n, a(n) for n = 1..300</a>

%F a(n) = Abs[numerator[Det[DiagonalMatrix[Table[(i+1)/(i+2)-1,{i,1,n}]]+1]]].

%t Abs[Numerator[Table[Det[DiagonalMatrix[Table[(i+1)/(i+2)-1,{i,1,n}]]+1],{n,1,70}]]]

%Y Cf. A118679, A038907.

%K frac,nonn

%O 1,1

%A _Alexander Adamchuk_, Jul 08 2006