%I A100015
%S A100015 2,3,43,481066515733,130850092279663
%N A100015 Subfactorial primes: primes of the form !n + 1 or !n - 1. Subfactorial 
               or rencontres numbers or derangements !n = A000166.
%D A100015 R. A. Brualdi and H. J. Ryser: Combinatorial Matrix Theory, 1992, Section 
               7.2, p. 202.
%D A100015 H. J. Ryser, Combinatorial Mathematics. Mathematical Association of America, 
               Carus Mathematical Monograph 14, 1963, p. 23. [J. V. Post was a student 
               of Herbert John Ryser (1923-1985) at Caltech.]
%H A100015 R. M. Dickau, <a href="http://mathforum.org/advanced/robertd/derangements.html">
               Derangement diagrams</a>.
%H A100015 H. Fripertinger, <a href="http://webdb.uni-graz.at/~fripert/fga/k1recontre.html">
               The Recontre Numbers</a>, an online calculator.
%H A100015 Mehdi Hassani, <a href="http://www.cs.uwaterloo.ca/journals/JIS/VOL6/
               Hassani/hassani5.html">Derangements and Applications</a>, Journal 
               of Integer Sequences, Vol. 6 (2003), #03.1.2
%F A100015 a(0) = 2 because !0 + 1 = 2.
%e A100015 a(5) = 130850092279663 because the 5+1 = 6th subfactorial prime is !17 
               - 1 = 130850092279664 - 1 = 130850092279663, which is prime. a(0) 
               = a(1) = 2 because !0 = !2 = 1, so !0 + 1 = !2 + 1 = 2.
%Y A100015 Cf. A000166, A000142, A002467, A008290, A003221, A000522, A000240, A000387, 
               A000449, A000475, A053871, A033030, A088991, A088992.
%Y A100015 Sequence in context: A162712 A062581 A077520 this_sequence A042819 A100443 
               A060415
%Y A100015 Adjacent sequences: A100012 A100013 A100014 this_sequence A100016 A100017 
               A100018
%K A100015 easy,nonn
%O A100015 1,1
%A A100015 Jonathan Vos Post (jvospost3(AT)gmail.com), Nov 18 2004