login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A293137 a(0) = 0, and a(n) = floor(2*sqrt(n)) - 1 for n >= 1. 2
0, 1, 1, 2, 3, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 18 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Conjecture: a(n) is index k of last nonzero entry in row n of A293136.

LINKS

Robert Israel, Table of n, a(n) for n = 0..10000

FORMULA

G.f.: (1-x)^(-1) * Sum_{k>=0} (x^(4*k^2+10*k+7)+x^((2*k+1)^2)+x^((2*k+2)^2)+x^(4*k^2+6*k+3)). - Robert Israel, Oct 01 2017

MAPLE

0, seq(seq(k, n=ceil(((k+1)/2)^2) .. ceil(((k+2)/2)^2)-1), k=0..18); # Robert Israel, Oct 01 2017

PROG

(PARI) a(n)=if(n==0, 0, floor(2*sqrt(n)) - 1);

CROSSREFS

Cf. A293136, A059618.

Sequence in context: A178042 A308950 A193832 * A087823 A230418 A037037

Adjacent sequences:  A293134 A293135 A293136 * A293138 A293139 A293140

KEYWORD

nonn

AUTHOR

Joerg Arndt, Oct 01 2017

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 January 16 15:53 EST 2021. Contains 340206 sequences. (Running on oeis4.)