OFFSET
1,2
COMMENTS
Since the absolute value of the discriminant of the characteristic polynomial is prime (=11), the sequence contains every nonnegative integer power of 11 (A001020 is subsequence). Other terms are formed on multiplication of 11^k by sporadic primes.
LINKS
Lars Blomberg, Table of n, a(n) for n = 1..65
C. Smyth, The Terms in Lucas Sequences Divisible by their Indices, Journal of Integer Sequences, Vol.13 (2010), Article 10.2.4
Wikipedia, Lucas sequence
EXAMPLE
u(1)=1 and u(11)=253. Clearly n divides u(n) for these terms.
MATHEMATICA
nn = 10000; s = LinearRecurrence[{1, -3}, {1, 1}, nn]; t = {}; Do[
If[Mod[s[[n]], n] == 0, AppendTo[t, n]], {n, nn}]; t (* T. D. Noe, Nov 06 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Thomas M. Bridge, Nov 02 2013
EXTENSIONS
a(27)-a(34) from Lars Blomberg, Feb 15 2016
STATUS
approved