0,3

Also (omitting initial 0) number of 1's in n-th row of triangle in A071039. - Hans Havermann (pxp(AT)rogers.com), May 26 2002

Binomial transform is A053220. - Michael Somos, Jul 10 2003

Smallest number of different people in a set of n-1 photographs which satisfies the following conditions: In each photograph there are 3 women, the woman in the middle is the mother of the person on her left and is a sister of the person on her right and the women in the middle of the photographs are all different. - Fung Cheok Yin (cheokyin_restart(AT)yahoo.com.hk), Sep 22 2006

A004396(a(n)) = n. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 30 2009]

International Mathematical Olympiad 2001, Hong Kong Preliminary Selection Contest Problem #20.

Index entries for sequences related to linear recurrences with constant coefficients

G.f.: (x+2*x^2)/((1-x)*(1-x^2)).

Formulae from Paul Barry (pbarry(AT)wit.ie), Sep 04 2003: a(n)=(6*n-1+(-1)^n)/4; a(n)=floor((3n+2)/2)-1 = A001651(n)-1; a(n)=sqrt(2)*sqrt((6n-1)(-1)^n+18n^2-6n+1)/4; a(n)=sum{k=0..n, 3/2-2*0^n+(-1)^n/2}.

a(n) = 3*floor(n/2) + n mod 2 = A007494(n)-A000035(n). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 04 2005

a(n)=2*A004526(n)+A004526(n+1). - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Aug 07 2006

a(n) = 1 + ceiling(1.5*(n-1)) - Fung Cheok Yin (cheokyin_restart(AT)yahoo.com.hk), Sep 22 2006

Row sums of triangle A133083. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Sep 08 2007

a(n) = (cos(Pi n) - 1)/4 + 1.5n [From Bart Snapp (snapp(AT)coastal.edu), Sep 18 2008]

a(n)=3*n-a(n-1)-5 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 21 2009]

For n=2, a(2)=3*2-0-5=1; n=3, a(3)=3*3-1-5=3; n=4, a(4)=3*4-3-5=4 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 21 2009]

a[0]:=0:a[1]:=1:for n from 2 to 100 do a[n]:=a[n-2]+3 od: seq(a[n], n=0..69); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 16 2008

seq(add(irem(2^k, 3), k=2..n), n=1..70); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 20 2008

Digits := 100: t := evalf(1+cos(Pi/3)): A:= n->floor(t*n): seq(floor((t*n)), n=0..69); # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 27 2009]

a[0]:=0:a[1]:=1:for n from 2 to 100 do a[n]:=a[n-2]+3 od: seq(a[n], n=0..69); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 16 2008

(PARI) a(n)=n+n\2.

For n>0, a(n)=T(n, 2), array T as in A049615. Column 1 of A026374.

Partial sums are A006578. Partial sums of A000034. Cf. A084056, A047270.

Cf. A001651, A007494, A035360, A132463.

Cf. A133083.

Sequence in context: A026322 A049624 A084056 this_sequence A064717 A109231 A140098

Adjacent sequences: A032763 A032764 A032765 this_sequence A032767 A032768 A032769

nonn,easy,nice,new

Patrick De Geest (pdg(AT)worldofnumbers.com), May 15, 1998.

Better description from N. J. A. Sloane (njas(AT)research.att.com) 8/98.