A141780 - OEIS

A141780

Numbers n such that A120292(n) is prime.

1, 4, 6, 10, 11, 12, 13, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 32, 33, 36, 37, 38, 40, 42, 44, 45, 46, 47, 48, 49, 52, 53, 54, 55, 57, 59, 60, 61, 62, 63, 64, 65, 68, 69, 72, 73, 74, 76, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 93, 94, 95, 99, 100, 102

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..70.

MATHEMATICA

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

PROG

(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

CROSSREFS

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.

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

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

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

Sequence in context: A349132 A057670 A171615 * A185002 A110604 A109270

Adjacent sequences: A141777 A141778 A141779 * A141781 A141782 A141783

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Jul 04 2008

STATUS

approved