This site is supported by donations to The OEIS Foundation.



Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A130779 a(0)=a(1)=1, a(2)=2, a(n)=0 for n >= 3. 7


%S 1,1,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

%T 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

%U 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

%N a(0)=a(1)=1, a(2)=2, a(n)=0 for n >= 3.

%C Inverse binomial transform of A002522. - _R. J. Mathar_, Jun 13 2008

%C Multiplicative with a(2)=2, a(2^e)=0 if e>1, a(p^e)=0 for odd prime p if e>=1. Dirichlet g.f. 1+2^(1-s). - _R. J. Mathar_, Jun 28 2011

%C a(n-1) is the determinant of the symmetric n X n matrix M(i,j) = rad(gcd(i,j)) for 1 <= i, j <= n, where rad(n) is the largest squarefree number dividing n (A007947). - _Amiram Eldar_, Jul 19 2019

%D J. Sándor and B. Crstici, Handbook of Number Theory II, Kluwer, 2004, p. 265.

%H <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1).

%F G.f.: 1+x+2x^2.

%F a(n) = [C((n+2)^2,n+4) mod 2]+[C((n+1)^2,n+3) mod 2]+2*[C(n^2,n+2) mod 2]. - _Paolo P. Lava_, Dec 19 2007

%F a(n) = A167666(n,0). - _Philippe Deléham_, Feb 18 2012

%t PadRight[{1,1,2},120,0] (* _Harvey P. Dale_, May 02 2015 *)

%t LinearRecurrence[{1},{1,1,2,0},105] (* _Ray Chandler_, Jul 15 2015 *)

%o (PARI) a(n)=if(n<3,max(n,1),0) \\ _Charles R Greathouse IV_, Dec 21 2011

%Y Cf. A002522, A007947, A130706, A167666.

%K nonn,mult,easy

%O 0,3

%A _Paul Curtz_, Jul 14 2007

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 12 12:50 EST 2019. Contains 329958 sequences. (Running on oeis4.)