A239831 Floor(7n^2/2) + floor(5n/2) + floor(3n/7).

5, 19, 39, 67, 101, 143, 191, 247, 308, 379, 454, 539, 628, 727, 830, 942, 1060, 1186, 1318, 1458, 1604, 1758, 1917, 2086, 2259, 2442, 2629, 2826, 3027, 3237, 3453, 3677, 3907, 4145, 4389, 4641, 4898, 5165, 5436, 5717, 6002, 6297, 6596, 6904, 7218, 7540

Offset: 1

Author

Katherine Guo, Mar 27 2014

Keywords

• nonn
• easy

Comments

This is a quadratic sequence.

Examples

			For n=3, a(3) = floor(7*3^2/2) + floor(5*3/2) + floor(3*3/7) = 39.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000
• Wolfram Alpha, Table of floor(7n^2/2) + floor(5n/2) + floor(3n/7).
• Index entries for linear recurrences with constant coefficients, signature (1,1,-1,0,0,0,1,-1,-1,1).

Programs

Magma

[Floor(7*n^2/2) + Floor(5*n/2) + Floor(3*n/7): n in [1..50]]; // Vincenzo Librandi, Mar 29 2014

Maple

A239831:=n->floor(7*n^2/2) + floor(5*n/2) + floor(3*n/7); seq(A239831(n), n=1..50); # Wesley Ivan Hurt, Mar 28 2014

Mathematica

Table[Floor[7 n^2/2] + Floor[5 n/2] + Floor[3 n/7], {n, 50}] (* Bruno Berselli, Mar 28 2014 *)

Formula

a(n) = (n(7n + 5) + (-1)^n - 1)/2 + A132270(3n + 1). [Bruno Berselli, Mar 28 2014]

a(n) = +a(n-1) +a(n-2) -a(n-3) +a(n-7) -a(n-8) -a(n-9) +a(n-10). [Bruno Berselli, Mar 28 2014]

Extensions

More terms from Bruno Berselli, Mar 28 2014