

A084741


Smallest prime of the form (n^k+1)/(n+1), or 0 if no such prime exists.


18



3, 7, 13, 521, 31, 43, 0, 73, 9091, 13421, 19141, 157, 7027567, 211, 241, 22796593, 307, 274019342889240109297, 152381, 421, 463, 39700406579747, 183458857, 601, 135938684703251, 0, 757, 574995877
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

2,1


COMMENTS

When n is a power (greater than 2) of a prime, then (n^k+1)/(n+1) will usually be composite for all k, which is the case for n = 8, 27, 32, 64, 125. The next term, a(30), is a 204digit number.  T. D. Noe, Jan 22 2004


LINKS

Table of n, a(n) for n=2..29.
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
R. G. Wilson, v, Letter to N. J. A. Sloane, circa 1991.


EXAMPLE

a(7)= 43 = (7^3 +1 )/(7+1) = 1  7 + 7^2 is a prime.


CROSSREFS

Cf. A084742 (least k such that (n^k+1)/(n+1) is prime).
Sequence in context: A221211 A322301 A154821 * A135623 A172291 A089305
Adjacent sequences: A084738 A084739 A084740 * A084742 A084743 A084744


KEYWORD

nonn


AUTHOR

Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 15 2003


EXTENSIONS

More terms from T. D. Noe, Jan 22 2004


STATUS

approved



