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 A073499 Numbers n such that n^(n+1) + (n+1)^n is prime. 6
 1, 2, 80, 342, 848, 1194, 2658, 4790, 9376 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS 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: A060051 A100421 A195000 * A222826 A123828 A260659 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

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