OFFSET
0,2
FORMULA
a(n) = ceiling(sqrt(3n+1)).
From Robert Israel, Nov 28 2016: (Start)
G.f.: (1-x)^(-1)*Sum_{k>=0} (x^(3*k^2)+x^(3*k^2+2*k+1)+x^(3*k^2+4*k+2)).
a(n+1) = a(n)+1 if n is in A032765, otherwise a(n+1) = a(n). (End)
MAPLE
seq(ceil(sqrt(3*k+1)), k=0..100); # Robert Israel, Nov 28 2016
MATHEMATICA
Table[Ceiling[Sqrt[3n+1]], {n, 0, 100}]
PROG
(Derive) PROG(y := [], n := 100, LOOP(IF(n = -1, RETURN y), y := ADJOIN(CEILING(SQRT(1 + 3·n)), y), n := n - 1))
(PARI) a(n)=sqrtint(3*n)+1 \\ Charles R Greathouse IV, Nov 29 2016
(Python)
from math import isqrt
def A278814(n): return 1+isqrt(3*n) # Chai Wah Wu, Jul 28 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Nov 28 2016
STATUS
approved