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A121258 a(n) = a(n-1)*a(n-2)*a(n-3) - 1 with a(0)=a(1)=a(2)=2. 3
2, 2, 2, 7, 27, 377, 71252, 725274107, 19482315963330427, 1006792136061113006060577048627 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

Analog of A055937 a(n) = a(n-1)*a(n-2) - 1. What is the equivalent continued fraction and asymptotic representation, by analogy to A007660 a(n) = a(n-1)*a(n-2) + 1?

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..14 (shortened by N. J. A. Sloane, Jan 13 2019)

FORMULA

a(n) ~ c^(A058265^n), where c = 1.3319334322065642848267... - Vaclav Kotesovec, Jun 15 2019

MATHEMATICA

RecurrenceTable[{a[0]==a[1]==a[2]==2, a[n] == a[n-1]*a[n-2]*a[n-3] - 1}, a, {n, 0, 15}] (* G. C. Greubel, Jun 07 2019 *)

PROG

(MAGMA) I:=[2, 2, 2]; [n le 3 select I[n] else Self(n-1)*Self(n-2)* Self(n-3)-1: n in [1..12]]; // Vincenzo Librandi, Nov 14 2011

(PARI) a(n) = if(n<3, 2, a(n-1)*a(n-2)*a(n-3) - 1);

vector(12, n, n--; a(n)) \\ G. C. Greubel, Jun 07 2019

(Sage)

def a(n):

    if (n==0 or n==1 or n==2): return 2

    else: return a(n-1)*a(n-2)*a(n-3) - 1

[a(n) for n in (0..12)] # G. C. Greubel, Jun 07 2019

CROSSREFS

Cf. A007660, A055937.

Sequence in context: A023573 A138757 A158927 * A087421 A309574 A132697

Adjacent sequences:  A121255 A121256 A121257 * A121259 A121260 A121261

KEYWORD

nonn,easy

AUTHOR

Jonathan Vos Post, Aug 22 2006

EXTENSIONS

Data corrected by Vincenzo Librandi, Nov 14 2011

STATUS

approved

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Last modified April 9 06:59 EDT 2020. Contains 333344 sequences. (Running on oeis4.)