A350190 Numbers k such that A083723(k) is prime.

1, 2, 3, 4, 5, 6, 15, 16, 17, 19, 20, 21, 22, 23, 28, 31, 34, 36, 39, 40, 42, 46, 49, 51, 52, 56, 63, 70, 72, 73, 75, 77, 81, 82, 86, 89, 90, 92, 96, 108, 112, 113, 115, 116, 117, 118, 129, 130, 132, 139, 145, 154, 156, 157, 164, 168, 169, 172, 181, 183, 184, 198, 201, 205, 206, 207, 213, 215

Offset

1,2

Comments

Numbers k such that k*prime(k)+k-1 is prime.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(7) = 15 is a term because A083723(15) = 15*47+14 = 719 is prime.

Maple

select(n -> isprime(n*ithprime(n)+n-1), [$1..1000]);

Mathematica

Select[Range[200], PrimeQ[(Prime[#] + 1)*# - 1] &] (* Amiram Eldar, Dec 19 2021 *)

Prog

(PARI) isok(k) = isprime(k*prime(k)+k-1); \\ Michel Marcus, Dec 19 2021

Crossrefs

Cf. A083723.

Sequence in context: A085157 A065637 A325805 * A039061 A138987 A318534

Adjacent sequences: A350187 A350188 A350189 * A350191 A350192 A350193

Keyword

nonn

Author

J. M. Bergot and Robert Israel, Dec 19 2021

Status

approved