OFFSET
1,1
COMMENTS
(a(n)-1)/2 gives indices of triangular numbers which are also pentagonal (A046175).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..200
Index entries for linear recurrences with constant coefficients, signature (14,-1).
FORMULA
a(n) = 14*a(n-1) - a(n-2).
G.f.: x*(3-x)/(1-14*x+x^2). - Bruno Berselli, May 03 2011
MATHEMATICA
LinearRecurrence[{14, -1}, {3, 41}, 19] (* Bruno Berselli, Nov 11 2011 *)
PROG
(Magma) [n le 2 select 38*n-35 else 14*Self(n-1)-Self(n-2): n in [1..19]]; // Bruno Berselli, May 03 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Sture Sjöstedt, May 02 2011
EXTENSIONS
Extended by T. D. Noe, May 02 2011
STATUS
approved