A229220 a(n) = a(n-1)^2 + (-1)^n with a(1)=1.

1, 2, 3, 10, 99, 9802, 96079203, 9231213249115210, 85215298050640192157847853344099, 7261647021859442133580964784539140878185975659356185857298121802

Offset

1,2

Comments

From the 4th element, the sum of the digits (modulo 9) of each term gives the sequence A000035.

Links

Table of n, a(n) for n=1..10.

Formula

a(n) ~ c^(2^n), where c = 1.15442119601942274770665172928641533277.... - Vaclav Kotesovec, Oct 09 2013

Maple

a := proc (n) if n = 1 then 1 else a(n-1)^2+(-1)^n end if end proc:
seq(a(i), i = 1 .. 10);

Mathematica

RecurrenceTable[{a[n] == a[n-1]^2 + (-1)^n, a[1]==1}, a, {n, 1, 10}] (* Vaclav Kotesovec, Oct 09 2013 *)

Prog

(PARI) a(n)=if(n==1, 1, a(n-1)^2+(-1)^n) \\ Charles R Greathouse IV, Sep 16 2013

Crossrefs

Cf. A000035.

Sequence in context: A184249 A270356 A333332 * A155148 A076927 A064647

Adjacent sequences: A229217 A229218 A229219 * A229221 A229222 A229223

Keyword

nonn

Author

Luca Finazzi, Sep 16 2013

Status

approved