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);
(Python)
from math import isqrt
def A293137(n): return isqrt(n<<2)-1 if n else 0 # Chai Wah Wu, Jul 28 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Joerg Arndt, Oct 01 2017
STATUS
approved