A143392 A quadratic recursion sequence: a(n)=a(n - 1)^2 - 2*a(n - 1) - a(n - 2)^2 + 2*a(n - 2).

1, 2, 1, -1, 4, 5, 7, 20, 325, 104615, 10943984020, 119770786197183303365, 14345041226291394498726932547331126324135, 205780207783999715270619814569860727079365052973702253248437750317796955577133460

Offset

1,2

Links

Table of n, a(n) for n=1..14.

Formula

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

log a(n) ~ 0.011287... * 2^n - Charles R Greathouse IV, Oct 06 2009

Mathematica

Clear[a, n]; a[0] = 1; a[1] = 2; a[n_] := a[n] = a[n - 1]^2 - 2*a[n - 1] - a[n - 2]^2 + 2*a[n - 2]; Table[a[n], {n, 0, 15}]
nxt[{a_, b_}]:={b, b^2-2b-a^2+2a}; NestList[nxt, {1, 2}, 15][[All, 1]] (* Harvey P. Dale, Aug 15 2021 *)

Crossrefs

Sequence in context: A078047 A329689 A270952 * A090668 A307977 A355334

Adjacent sequences: A143389 A143390 A143391 * A143393 A143394 A143395

Keyword

sign

Author

Roger L. Bagula and Gary W. Adamson, Oct 23 2008

Extensions

Corrected by Harvey P. Dale, Aug 15 2021

Status

approved