A167822 Subsequence of A167709 whose indices are congruent to 1 mod 5, i.e., a(n) = A167709(5*n+1).

1, 560, 190399, 64735100, 22009743601, 7483248089240, 2544282340597999, 865048512555230420, 294113949986437744801, 99997877946876278001920, 33998984387987948082907999, 11559554694037955471910717740, 3930214596988516872501561123601

Offset

0,2

Links

G. C. Greubel, Table of n, a(n) for n = 0..100

Index entries for linear recurrences with constant coefficients, signature (340,-1).

Formula

a(n+2) = 340*a(n+1) - a(n).

a(n+1) = 170*a(n) + 39*sqrt(19*(a(n))^2 + 81).

G.f.: (1 + 220*z)/(1 - 340*z + z^2).

a(n) = (10*sqrt(19) + 19)/38*(170 + 39*sqrt(19))^n + (-10*sqrt(19) + 19)/38*(170 - 39*sqrt(19))^n.

Example

a(0) = A167709(1) = 1, a(1) = A167709(6) = 560.

Maple

w(0):=1:for n from 0 to 20 do w(n+1):=170*w(n)+39*sqrt(19*(w(n))^2+81) :od: seq(w(n), n=0..20); for n from 0 to 20 do u(n):=simplify((10*sqrt(19)+19)/38*(170+39*sqrt(19))^(n)+(-10*sqrt(19)+19)/38*(170-39*sqrt(19))^(n)):od:seq(u(n), n=0..20); taylor(((1+560*z-1*340*z)/(1-340*z+z^2)), z=0, 21);

Mathematica

LinearRecurrence[{340, -1}, {1, 560}, 50] (* G. C. Greubel, Jun 27 2016 *)
RecurrenceTable[{a[1] == 1, a[2] == 560, a[n] == 340 a[n-1] - a[n-2]}, a, {n, 15}] (* Vincenzo Librandi, Jun 28 2016 *)

Prog

(Magma) I:=[1, 560]; [n le 2 select I[n] else 340*Self(n-1)-Self(n-2): n in [1..30]]; // Vincenzo Librandi, Jun 28 2016

Crossrefs

Sequence in context: A193171 A013487 A229389 * A104590 A259211 A265261

Adjacent sequences: A167819 A167820 A167821 * A167823 A167824 A167825

Keyword

easy,nonn

Author

Richard Choulet, Nov 13 2009

Status

approved