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

Author

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

Keywords

• nonn
• easy

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).

Crossrefs

Cf. A131029, A131074.

Programs

Magma

m:=84; [ [15, 11, 5, 1, 1, 5, 11, 15][(n-1) mod 8 + 1]: n in [1..m] ];

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 *)

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))), ","))}

Scheme

(define (A131082 n) (list-ref '(15 11 5 1 1 5 11 15) (modulo (- n 1) 8))) ;; Antti Karttunen, Aug 10 2017

Formula

a(n) = a(n-8).

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