A084830 Numbers n such that (n!)^2 + n! - 1 is prime.

2, 3, 4, 5, 6, 14, 17, 50, 111, 254, 506

Offset

1,1

References

H. Dubner, Factorial and primorial primes, J. Rec. Math., 19 (No. 3, 1987).

Links

Table of n, a(n) for n=1..11.

Dorin Andrica, George C. Ţurkaş, An elliptic Diophantine equation from the study of partitions, Stud. Univ. Babeş-Bolyai Math. (2019) Vol. 64, No. 3, 349-356.

Example

5 is in the sequence because (5!)^2+5!-1=14519 is prime.

Mathematica

Do[If[PrimeQ[n!^2+n!-1], Print[n]], {n, 600}]

Crossrefs

Cf. A002981, A002982.

Sequence in context: A039016 A249102 A250047 * A116044 A116027 A085157

Adjacent sequences: A084827 A084828 A084829 * A084831 A084832 A084833

Keyword

more,nonn

Author

Farideh Firoozbakht, Jul 12 2003

Status

approved