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A131028
Periodic sequence (7, 4, 1, 1, 4, 7).
10
7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1, 1, 4, 7, 7, 4, 1
OFFSET
1,1
COMMENTS
Fourth column of triangular array T defined in A131022.
Continued fractions of (131 + sqrt(18530))/37 = 7.2195930... - R. J. Mathar, Mar 08 2012
FORMULA
a(1) = a(6) = 7, a(2) = a(5) = 4, a(3) = a(4) = 1; for n > 6, a(n) = a(n-6).
G.f.: x*(7-10*x+7*x^2)/((1-x)*(1-x+x^2)).
a(n) = A084104(n+2).
a(n) = 4+2*sqrt(3)*cos(Pi/6*(2*n-1)). - Werner Schulte, Jul 21 2017
MATHEMATICA
PadRight[{}, 120, {7, 4, 1, 1, 4, 7}] (* Harvey P. Dale, Jul 15 2013 *)
PROG
(PARI) {m=105; for(n=1, m, r=(n-1)%6; print1(if(r==0||r==5, 7, if(r==1||r==4, 4, 1)), ", "))}
(Magma) m:=105; [ [7, 4, 1, 1, 4, 7][(n-1) mod 6 + 1]: n in [1..m] ];
CROSSREFS
Cf. A131022, A084104. Other columns of T are in A088911, A131026, A131027, A131029, A131030.
Sequence in context: A082665 A011101 A021935 * A225463 A010138 A371851
KEYWORD
nonn,easy
AUTHOR
Klaus Brockhaus, following a suggestion of Paul Curtz, Jun 10 2007
STATUS
approved