login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A105613 Self-convolution omits 1's at positions of triangular numbers less one. 1
1, 1, 1, 2, 3, 1, 6, 11, 12, 1, 24, 48, 71, 78, 1, 155, 272, 420, 652, 903, 1, 1364, 2144, 3436, 5955, 9668, 10838, 1, 16408, 27948, 45920, 66817, 109296, 152786, 197542, 1, 327755, 531440, 735565, 1083128, 1727206, 2521374, 3938246, 5248706, 1, 8452114 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Self-convolution is A105614.

LINKS

Table of n, a(n) for n=0..45.

EXAMPLE

Given this sequence:

A = [1, 1, 1, 2,3, 1, 6,11,12, 1, 24,48,71,78, 1, 155, ...],

the self-convolution yields:

A^2 = [1, 2,3, 6,11,12, 24,48,71,78, 155,272,420,652,903, ...],

giving this sequence with 1's omitted at positions {0,2,5,9,14,...}.

PROG

(PARI) a(n)=local(V, t); if(n==0 || n==1, 1, t=ceil((sqrt(8*n+9)-1)/2); if(ceil((sqrt(8*n+17)-1)/2)-t==1, 1, V=vector(n-t+2, k, a(k-1)); polcoeff(Ser(V)^2+O(x^(n-t+2)), n-t+1)))

CROSSREFS

Cf. A105614.

Sequence in context: A008275 A130534 A107416 * A263634 A135894 A247500

Adjacent sequences:  A105610 A105611 A105612 * A105614 A105615 A105616

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Apr 16 2005

STATUS

approved

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 February 16 14:47 EST 2019. Contains 320163 sequences. (Running on oeis4.)