A204321 Start with 4. Square the previous term and subtract it.

4, 12, 132, 17292, 298995972, 89398590973228812, 7992108067998667938125889533702532, 63873791370569400659097694858350356285036046451665934814399129508492

Offset: 1

Author

Daniel Chiverton, Jan 14 2012

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..11
• J. A. Haddley, Doubling Hypercuboids, Preprint 2015.

Programs

Maple

A204321 := proc(n)
        if n = 1 then
                4;
        else
                procname(n-1)*(procname(n-1)-1) ;
        end if;
end proc:
seq(A204321(n),n=1..10) ; # R. J. Mathar, Jan 19 2012

Mathematica

Join[{a = 4}, Table[a = a^2 - a, {n, 9}]] (* Vladimir Joseph Stephan Orlovsky, Feb 24 2012 *)
RecurrenceTable[{a[1]==4, a[n] == a[n-1]*(a[n-1]-1)}, a, {n, 1, 10}] (* Vaclav Kotesovec, Dec 18 2014 *)
NestList[#^2-#&,4,10] (* Harvey P. Dale, Jun 20 2023 *)

Formula

a(n) = a(n-1)*(a(n-1)-1).

a(n) ~ c^(2^n), where c = 1.8401979467004699327247921093647566233474761412868967823409865843403604499... . - Vaclav Kotesovec, Dec 18 2014