A131082 Periodic sequence (15, 11, 5, 1, 1, 5, 11, 15).

15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1, 1, 5, 11, 15, 15, 11, 5, 1

Offset

1,1

Comments

Fifth column of triangular array T defined in A131074.

Simple continued fraction of (1728521 + sqrt(3040737300437))/230114 = 15.0894426240... - R. J. Mathar, Mar 08 2012

Links

Antti Karttunen, Table of n, a(n) for n = 1..8192

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

Formula

a(1) = a(8) = 15, a(2) = a(7) = 11, a(3) = a(6) = 5, a(4) = a(5) = 1; for n > 8, a(n) = a(n-8).

G.f.: (15 - 4*x - 6*x^2 - 4*x^3 + 15*x^4)/((1-x)*(1+x^4)).

a(n) = (1/28)*{8*(n mod 8) - 6*((n+1) mod 8) - 13*((n+2) mod 8) - 6*((n+3) mod 8) + 8*((n+4) mod 8) + 22*((n+5) mod 8) + 29*((n+6) mod 8) + 22*((n+7) mod 8)), with n >= 0. - Paolo P. Lava, Jun 19 2007

Mathematica

PadRight[{}, 100, {15, 11, 5, 1, 1, 5, 11, 15}] (* or *) LinearRecurrence[ {1, 0, 0, -1, 1}, {15, 11, 5, 1, 1}, 100] (* Harvey P. Dale, Feb 01 2015 *)

Prog

(PARI) {m=84; for(n=1, m, r=(n-1)%8; print1(if(r==0||r==7, 15, if(r==1||r==6, 11, if(r==2||r==5, 5, 1))), ", "))}
(Magma) m:=84; [ [15, 11, 5, 1, 1, 5, 11, 15][(n-1) mod 8 + 1]: n in [1..m] ];
(Scheme) (define (A131082 n) (list-ref '(15 11 5 1 1 5 11 15) (modulo (- n 1) 8))) ;; Antti Karttunen, Aug 10 2017

Crossrefs

Cf. A131029, A131074.

Sequence in context: A013449 A013461 A013430 * A296818 A097953 A200522

Adjacent sequences: A131079 A131080 A131081 * A131083 A131084 A131085

Keyword

nonn,easy

Author

Klaus Brockhaus, following a suggestion of Paul Curtz, Jun 14 2007

Status

approved