0,3

Gives the (zero-based) positions of odd terms in A007556 (Mod[A007556[A0023001(n)],2]=1). - Farideh_Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Jun 13 2003

a(n) = A033138(3n-2). - Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), May 31 2005

{1, 9, 73, 585, 4681, ...} is the binomial transform of A003950 . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Jul 22 2005

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

Also sum of cubes of divisors of 2^(n-1): a(n)=A001158[A000079(n-1)] - Labos E. (labos(AT)ana.sote.hu), Apr 10 2003, and Farideh_Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Jun 13 2003

a(0)=0, a(n)=8*a(n-1)+1 for n>0 . G.f.:x/((1-8x)*(1-x)) - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 12 2006

Octal.............decimal (comment from Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 14 2007):

0....................0

1....................1

11...................9

111.................73

1111...............585

11111.............4681

111111...........37449

1111111.........299593

11111111.......2396745

111111111.....19173961

1111111111...153391689

etc. ...............etc.

a:=n->sum(8^(n-j), j=1..n): seq(a(n), n=0..20); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 04 2007

Table[(8^n-1)/7, {n, 0, m}]

Cf. A007556.

Sequence in context: A079927 A126641 A081627 this_sequence A015454 A121246 A086226

Adjacent sequences: A022998 A022999 A023000 this_sequence A023002 A023003 A023004

easy,nonn

David W. Wilson (davidwwilson(AT)comcast.net)