A178936 a(n) = floor((2*3^n+3*2^n)/5).

1, 2, 6, 15, 42, 116, 330, 951, 2778, 8180, 24234, 72087, 215034, 642644, 1923018, 5759223, 17258010, 51734708, 155125482, 465219159, 1395342906, 4185399572, 12554940426, 37662304695, 112981880922, 338935576436, 1016786596650, 3050319524631, 9150878043258

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..2000

Index entries for linear recurrences with constant coefficients, signature (5,-6,0,1,-5,6).

Formula

G.f.: (1-3*x+2*x^2-3*x^3+2*x^4-x^5)/(1-5*x+6*x^2-x^4+5*x^5-6*x^6) = (1-3*x+2*x^2-3*x^3+2*x^4-x^5)/((1-2*x)*(1-3*x)*(1-x^4)).

Recurrence: a(n+6) = 5*a(n+5)-6*a(n+4)+a(n+2)-5*a(n+1)+6*a(n).

a(n) = (8*3^n+12*2^n-(1-(-1)^n)*(5+i^(n+1)))/20, where i=sqrt(-1). - Bruno Berselli, Sep 05 2011

Prog

(Maxima) makelist(floor((2*3^n+3*2^n)/5), n, 0, 12);
(Magma) [Floor((2*3^n+3*2^n)/5): n in [0..30]]; // Vincenzo Librandi, Sep 06 2011

Crossrefs

Cf. A178934, A178935.

Sequence in context: A280782 A307308 A065178 * A221744 A338861 A340726

Adjacent sequences: A178933 A178934 A178935 * A178937 A178938 A178939

Keyword

nonn,easy

Author

Emanuele Munarini, Dec 30 2010

Status

approved