login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A131779 Triangle read by rows: T(n,k) = 2*A065941(n-1,k-1) - (-1)^(n+k). 3
1, 3, 1, 1, 3, 1, 3, 1, 5, 1, 1, 3, 5, 5, 1, 3, 1, 9, 5, 7, 1, 1, 3, 9, 9, 11, 7, 1, 3, 1, 13, 9, 21, 11, 9, 1, 1, 3, 13, 13, 29, 21, 19, 9, 1, 3, 1, 17, 13, 43, 29, 41, 19, 11, 1, 1, 3, 17, 17, 55, 43, 69, 41, 29, 11, 1, 3, 1, 21, 17, 73, 55, 113, 69, 71, 29, 13, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1275 (first 50 rows)
FORMULA
T(n,k) = 2*binomial(n-1-floor(k/2), floor((k-1)/2)) - (-1)^(n+k). - Andrew Howroyd, Sep 08 2018
EXAMPLE
First few rows of the triangle are:
1;
3, 1;
1, 3, 1;
3, 1, 5, 1;
1, 3, 5, 5, 1;
3, 1, 9, 5, 7, 1;
1, 3, 9, 9, 11, 7, 1;
...
PROG
(PARI) T(n, k) = {if(k<=n, 2*binomial(n-1-k\2, (k-1)\2) - (-1)^(n+k), 0)} \\ Andrew Howroyd, Sep 08 2018
CROSSREFS
Row sums are A131780.
Cf. A065941.
Sequence in context: A193179 A133705 A046111 * A131775 A218825 A035691
KEYWORD
nonn,tabl
AUTHOR
Gary W. Adamson, Jul 14 2007
EXTENSIONS
a(28)-a(29) corrected and terms a(56) and beyond from Andrew Howroyd, Sep 08 2018
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 3 22:39 EDT 2023. Contains 365872 sequences. (Running on oeis4.)