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A130779 a(0)=a(1)=1, a(2)=2, a(n)=0 for n >= 3. 7
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, 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, 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Inverse binomial transform of A002522. - R. J. Mathar, Jun 13 2008

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

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

REFERENCES

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

LINKS

Table of n, a(n) for n=0..104.

Index entries for linear recurrences with constant coefficients, signature (1).

FORMULA

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

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

a(n) = A167666(n,0). - Philippe Deléham, Feb 18 2012

MATHEMATICA

PadRight[{1, 1, 2}, 120, 0] (* Harvey P. Dale, May 02 2015 *)

LinearRecurrence[{1}, {1, 1, 2, 0}, 105] (* Ray Chandler, Jul 15 2015 *)

PROG

(PARI) a(n)=if(n<3, max(n, 1), 0) \\ Charles R Greathouse IV, Dec 21 2011

CROSSREFS

Cf. A002522, A007947, A130706, A167666.

Sequence in context: A063665 A276306 A072507 * A130706 A000038 A228594

Adjacent sequences:  A130776 A130777 A130778 * A130780 A130781 A130782

KEYWORD

nonn,mult,easy

AUTHOR

Paul Curtz, Jul 14 2007

STATUS

approved

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Last modified October 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)