A248198 a(n) = ceiling(n^3*(Pi/2)).

2, 13, 43, 101, 197, 340, 539, 805, 1146, 1571, 2091, 2715, 3452, 4311, 5302, 6434, 7718, 9161, 10775, 12567, 14548, 16726, 19112, 21715, 24544, 27609, 30918, 34483, 38311, 42412, 46796, 51472, 56450, 61739, 67348, 73288, 79566, 86193, 93179, 100531

Offset: 1

Author

Juliann Barbella, Oct 03 2014

Keywords

• nonn
• easy

Comments

a(n) is the ceiling of the area of a square with diagonal n times the circumference of a circle with diameter n. - Wesley Ivan Hurt, Oct 03 2014

a(n) is also the ceiling of the volume of a cylinder with radius n and height n/2. Equivalently, a(n) is the ceiling of the volume of a cylinder with diameter n and height 2*n. - Derek Orr, Oct 03 2014

Crossrefs

Cf. A228391 (similar, with floor).

Programs

Java

int a(int n) {return (int) Math.ceil(Math.pow(n, 3)*Math.PI/(2)); }

Maple

A248198:=n->ceil(n^3*(Pi/2)): seq(A248198(n), n=1..40); # Wesley Ivan Hurt, Oct 03 2014

Mathematica

Table[Ceiling[n^3*(Pi/2)], {n, 40}] (* Wesley Ivan Hurt, Oct 03 2014 *)

PARI

vector(100,n,ceil(n^3*Pi/2)) \\ Derek Orr, Oct 03 2014