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A067359 Real part of (5+12i)^n. 3
1, 5, -119, -2035, -239, 341525, 3455641, -23161315, -815616479, -4241902555, 95420159401, 1671083125805, 584824319281, -276564805068235, -2864483360640839, 18094618450123325, 665043872449535041, 3592448206424508485, -76467932379726337079, -1371803070683005304755 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also 13^n cos(2n arctan(2/3)) or denominator of tan(2n arctan(2/3)).

Note that A067358(n), a(n) and 13^n are primitive Pythagorean triples with hypotenuse 13^n.

REFERENCES

Steven R. Finch, Mathematical Constants, Cambridge, 2003, pp. 430-433.

LINKS

Table of n, a(n) for n=1..20.

J. M. Borwein and R. Girgensohn, Addition theorems and binary expansions, Canadian J. Math. 47 (1995) 262-273.

E. Eckert, The group of primitive Pythagorean triangles, Mathematics Magazine 57 (1984) 22-27.

Steven R. Finch, Plouffe's Constant [Broken link]

Steven R. Finch, Plouffe's Constant [From the Wayback machine]

Simon Plouffe, The Computation of Certain Numbers Using a Ruler and Compass, J. Integer Seqs. Vol. 1 (1998), #98.1.3.

FORMULA

G.f.: (1-5*x)/(1-10*x+169*x^2). a(n)=10*a(n-1)-169*a(n-2). - Michael Somos, Jun 27 2002

a(n)=(1/2)*[(5-12*I)^n+(5+12*I)^n], with n>=0 and I=sqrt(-1) - Paolo P. Lava, Jul 15 2008

MAPLE

a[1] := 12/5; for n from 1 to 40 do a[n+1] := (12/5+a[n])/(1-12/5*a[n]):od: seq(abs(denom(a[n])), n=1..40); # a[n]=tan(2n arctan(2/3))

MATHEMATICA

Table[Re[(5+12I)^n], {n, 0, 20}] (* Harvey P. Dale, Aug 24 2014 *)

PROG

(PARI) a(n)=real((5+12*I)^n)

CROSSREFS

Cf. A067358 (13^n sin(2n arctan(2/3))).

Cf. A066770, A066771, A067360, A067361, A020888, A014498, A020892.

Sequence in context: A144998 A257865 A212040 * A156962 A065818 A139189

Adjacent sequences:  A067356 A067357 A067358 * A067360 A067361 A067362

KEYWORD

sign,easy,frac

AUTHOR

Barbara Haas Margolius, (b.margolius(AT)csuohio.edu), Jan 17 2002

EXTENSIONS

Better description from Michael Somos, Jun 27 2002

STATUS

approved

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Last modified May 19 14:45 EDT 2019. Contains 323395 sequences. (Running on oeis4.)