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Numbers n such that A120292(n) is prime.
3

%I #9 May 11 2020 02:32:22

%S 1,4,6,10,11,12,13,18,19,20,21,22,24,25,26,27,28,29,30,32,33,36,37,38,

%T 40,42,44,45,46,47,48,49,52,53,54,55,57,59,60,61,62,63,64,65,68,69,72,

%U 73,74,76,78,79,80,81,82,83,84,85,86,87,88,89,90,91,93,94,95,99,100,102

%N Numbers n such that A120292(n) is prime.

%t Select[Range[200],PrimeQ[Numerator[Abs[(1 - Sum[Prime[k] + 1,{k, 1, #}])/Product[Prime[k] + 1, {k, 1, #}] ]]]&]

%o (PARI) isok(n) = isprime(abs(numerator(matdet(matrix(n, n, i, j, if(i==j, prime(i)/(1+prime(i)), 1)))))); \\ _Michel Marcus_, May 10 2020

%Y Cf. A120292 = absolute value of the numerator of the determinant of n X n matrix M with M[i, j] = prime[i]/(1 + prime[i]) if i = j, and 1 otherwise.

%Y Cf. A125716 = numbers n such that A120292(n) = 1.

%Y Cf. A141779 = numbers n such that A120292(n) > 1 and is not prime.

%Y Cf. A141781 = terms of A120292 that are greater than 1 and are not prime; or A120292(A141779).

%K nonn

%O 1,2

%A _Alexander Adamchuk_, Jul 04 2008