A184019 A (9,-5) Somos-4 sequence

1, 2, 13, 97, 901, 29186, 1647721, 93837697, 12290566873, 4736355079682, 1969233690270421, 1126004701770879841, 2327721451902521875261, 7371705459667139440634882, 24178816113044965430498802193, 208545961878958994572139555513857, 4688266673793881234527843412398379761

Offset

0,2

Comments

Hankel transform of A184018.

Links

G. C. Greubel, Table of n, a(n) for n = 0..75

Formula

a(n) = (9*a(n-1)*a(n-3) - 5*a(n-2)^2)/a(n-4).

Mathematica

a[n_] := a[n] = (9 a[n - 1] a[n - 3] - 5 a[n - 2]^2)/a[n - 4]; a[0] = 1; a[1] = 2; a[2] = 13; a[3] = 97; Array[a, 17, 0]
RecurrenceTable[{a[0]==1, a[1]==2, a[2]==13, a[3]==97, a[n]==(9a[n-1]a[n-3]- 5a[n-2]^2)/a[n-4]}, a[n], {n, 20}] (* Harvey P. Dale, Sep 06 2011 *)

Prog

(Magma) I:=[901, 29186, 1647721, 93837697]; [1, 2, 13, 97] cat [n le 4 select I[n] else (9*Self(n-1)*Self(n-3) - 5*Self(n-2)^2)/Self(n-4): n in [1..30]]; // G. C. Greubel, Aug 14 2018

Crossrefs

Sequence in context: A118352 A320360 A074614 * A300633 A340451 A064325

Adjacent sequences: A184016 A184017 A184018 * A184020 A184021 A184022

Keyword

nonn

Author

Paul Barry, Jan 08 2011

Status

approved