A248469 a(n) = floor((2*n^2)/e).

0, 2, 6, 11, 18, 26, 36, 47, 59, 73, 89, 105, 124, 144, 165, 188, 212, 238, 265, 294, 324, 356, 389, 423, 459, 497, 536, 576, 618, 662, 707, 753, 801, 850, 901, 953, 1007, 1062, 1119, 1177, 1236, 1297, 1360, 1424, 1489, 1556, 1625, 1695, 1766, 1839

Offset: 1

Author

Juliann Barbella, Oct 06 2014

Keywords

• nonn
• easy

Crossrefs

Cf. A032635 (floor(n^2/e)).

Programs

Java

int a(int n) {return (int) ((2*Math.pow(x, 2))/Math.exp(1.0)); }

Mathematica

Table[Floor[(2 n^2)/ E ], {n, 1, 60}] (* Vincenzo Librandi, Oct 23 2014 *)

PARI

a(n) = (2*n^2)\exp(1) \\ Michel Marcus, Oct 25 2014

Formula

a(n) = floor((2*n^2)/e).

Extensions

More terms from Vincenzo Librandi, Oct 23 2014