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 A056788 a(n) = n^n + (n-1)^(n-1). 10

%I

%S 2,5,31,283,3381,49781,870199,17600759,404197705,10387420489,

%T 295311670611,9201412118867,311791207040509,11414881932150269,

%U 449005897206417391,18884637964090410991,845687005960046315793

%N a(n) = n^n + (n-1)^(n-1).

%C For even n > 1, the absolute value of the discriminant of the polynomial x^n+x-1. [Corrected by _Artur Jasinski_, May 07 2010]

%C The largest known prime in this sequence is a(4) = 283.

%D R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see equation (6.7).

%H Walter Nissen, <a href="http://upforthecount.com/math/nnpomega.html">post on np ( n ) = n^n + (n+1)^(n+1)</a>, on home page <a href="http://upforthecount.com">"Up for the count!"</a>. (Updated Oct 02 2012)

%e a(3) = 2^2 + 3^3 = 4 + 27 = 31.

%t Join[{2}, Table[n^n+(n-1)^(n-1), {n, 2, 20}]] (* _T. D. Noe_, Aug 13 2004 *)

%t Join[{2},Total/@Partition[Table[n^n,{n,20}],2,1]] (* _Harvey P. Dale_, Jun 26 2017 *)

%o (PARI) A056788(n)=n^n+(n-1)^(n-1) \\ _M. F. Hasler_, Oct 02 2012

%Y Cf. A000312 (n^n), A086797 (discriminant of the polynomial x^n-x-1).

%Y Cf. A056187, A056790, A192397 (smallest & largest prime factor of a(n), records of the latter), A217435 = bigomega(a(n)).

%K nonn

%O 1,1

%A _Walter Nissen_, Aug 20 2000

%E Minor corrections by _M. F. Hasler_, Oct 02 2012

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Last modified September 19 23:59 EDT 2019. Contains 327207 sequences. (Running on oeis4.)