0,3

Complement of A002265, since 4*A002265(n)+a(n)=n. - Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), Jun 01 2007

The rightmost digit in the base-4 representation of n. Also, the equivalent value of the two rightmost digits in the base-2 representation of n. - Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), Jun 11 2007

a(n) = n mod 4

a(n)=(1/2)*(3-(-1)^n-2*(-1)^floor(n/2)); also a(n)=(1/2)*(3-(-1)^n-2*(-1)^((2n-1+(-1)^n)/4))); also a(n)=(1/2)*(3-(-1)^n-2*sin(pi/4*(2n+1+(-1)^n))). G.f.: g(x)=(3x^3+2x^2+x)/(1-x^4). - Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), May 29 2007

Trigonometric representation: a(n)=2^2*(sin(n*pi/4))^2*sum{1<=k<4, k*product{1<=m<4,m<>k, (sin((n-m)*pi/4))^2}}. Clearly, the squared terms may be replaced by their absolute values '|.|'. Complex representation: a(n)=1/4*(1-r^n)*sum{1<=k<4, k*product{1<=m<4,m<>k, (1-r^(n-m))}} where r=exp(pi/2*i)=i=sqrt(-1). All these formulas can be easily adapted to represent any periodic sequence. G.f.: also g(x)=x(4x^5-5x^4+1)/((1-x^4)(1-x)^2). - Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), Jun 01 2007

a(n)=n mod 2+2*(floor(n/2)mod 2)=A000035(n)+2*A000035(A004526(n)). - Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), Jun 11 2007

a(n) = 6 - a(n-1) - a(n-2) - a(n-3) for n > 2. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 13 2008

Partial sums: A130482. Other related sequences A130481, A130483, A130484, A130485.

Cf. A004526, A002264, A002265, A002266.

Adjacent sequences: A010870 A010871 A010872 this_sequence A010874 A010875 A010876

Sequence in context: A030386 A096799 A106728 this_sequence A049804 A132387 A124757

nonn

njas