A115519 n*(1+3*n+6*n^2)/2.

0, 5, 31, 96, 218, 415, 705, 1106, 1636, 2313, 3155, 4180, 5406, 6851, 8533, 10470, 12680, 15181, 17991, 21128, 24610, 28455, 32681, 37306, 42348, 47825, 53755, 60156, 67046, 74443, 82365, 90830, 99856, 109461, 119663, 130480, 141930, 154031, 166801, 180258

Offset

0,2

Links

Table of n, a(n) for n=0..39.

Formula

a(n) = n*(1+3*n+6*n^2)/2. a(n) = n*A085473(n)/2. a(n) = n*[C(2n+3,3)-C(2n,3)]/2. - Jonathan Vos Post, Mar 10 2006

a(0) = 0, a(1) = 5, a(2) = 31, a>2: a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + 18; G.f. = (5*x+11*x^2+2*x^3)/(1-x)^4 - Zak Seidov, Mar 10 2006

Crossrefs

Cf. A085473.

Sequence in context: A138657 A106909 A304659 * A211923 A362304 A024399

Adjacent sequences: A115516 A115517 A115518 * A115520 A115521 A115522

Keyword

nonn

Author

N. J. A. Sloane, Mar 09 2006

Status

approved