A073499 Numbers n such that n^(n+1) + (n+1)^n is prime.

1, 2, 80, 342, 848, 1194, 2658, 4790, 9376

Offset

1,2

Links

Table of n, a(n) for n=1..9.

P. Leyland, Primes and Strong Pseudoprimes of the form x^y + y^x - The numbers corresponding to the first 7 terms had been proved prime by 2005.

Example

1^2 + 2^1 = 3 and 2^3 + 3^2 = 17 are the primes corresponding to the first two terms. The next five terms correspond to primes of 155, 870, 2487, 3678 and 9106 decimal digits.

Mathematica

Do[ If[ PrimeQ[n^(n + 1) + (n + 1)^n], Print[n]], {n, 1, 1650}]

Prog

(PARI) for(n=1, 1650, if(isprime((n^(n+1))+((n+1)^n)), print1(n, ", ")))

Crossrefs

Cf. A072179, A051442, A094133.

Sequence in context: A319438 A371151 A195000 * A378312 A222826 A123828

Adjacent sequences: A073496 A073497 A073498 * A073500 A073501 A073502

Keyword

nonn,hard

Author

Rick L. Shepherd, Aug 05 2002

Extensions

Edited by Robert G. Wilson v, Aug 08 2002

a(7) from Charles R Greathouse IV, Jan 13 2012

a(8) from Charles R Greathouse IV, Jan 17 2012

a(9) found by Alexander Adamchuk, Apr 09 2007 and shown to be a(9) by Charles R Greathouse IV, Jan 27 2012

Status

approved