OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,1,-1).
FORMULA
a(n) = 7*n - a(n-1) - 7, with n>1, a(1)=0.
G.f.: 7*x^2/((1+x)*(1-x)^2). - Bruno Berselli, Sep 17 2013
a(n) = 7*A004526(n). - Bruno Berselli, Sep 17 2013
E.g.f.: (7/2)*(x*cosh(x) + (x - 1)*sinh(x)). - G. C. Greubel, Jul 19 2016
MATHEMATICA
CoefficientList[Series[7 x/((1 + x) (1 - x)^2), {x, 0, 70}], x] (* Vincenzo Librandi, Sep 17 2013 *)
Table[7 Floor[n/2], {n, 60}] (* Bruno Berselli, Sep 18 2013 *)
PROG
(Magma) [n eq 1 select 0 else 7*n-Self(n-1)-7: n in [1..70]]; // Vincenzo Librandi, Sep 17 2013
CROSSREFS
KEYWORD
nonn,easy,less
AUTHOR
Vincenzo Librandi, Nov 24 2009
EXTENSIONS
New definition by Bruno Berselli, Sep 18 2013
STATUS
approved