A047866 a(n) = ceiling(n*(n+1)*(n+2)/8).

0, 1, 3, 8, 15, 27, 42, 63, 90, 124, 165, 215, 273, 342, 420, 510, 612, 727, 855, 998, 1155, 1329, 1518, 1725, 1950, 2194, 2457, 2741, 3045, 3372, 3720, 4092, 4488, 4909, 5355, 5828, 6327, 6855, 7410, 7995, 8610, 9256, 9933, 10643, 11385

Offset

0,3

Comments

A lower bound to Honaker's triangle problem A047837.

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..10000

Index entries for linear recurrences with constant coefficients, signature (3,-3,1,0,0,0,0,1,-3,3,-1).

Formula

G.f.: x*(1 + 2*x^2 - x^3 + 3*x^4 - 2*x^5 + 3*x^6)/((1-x)^4*(1+x)*(1+x^2)*(1+x^4)). - R. J. Matharq, Mar 11 2012

Prog

(Magma) [Ceiling( n*(n+1)*(n+2)/8 ) : n in [0..50]]; // Vincenzo Librandi, Sep 28 2011
(PARI) a(n)=(n*(n+1)*(n+2)+6)\8 \\ Charles R Greathouse IV, Oct 07 2015

Crossrefs

Cf. A047837.

Sequence in context: A049717 A241565 A359210 * A080183 A109900 A034828

Adjacent sequences: A047863 A047864 A047865 * A047867 A047868 A047869

Keyword

nonn,easy

Author

Mike Keith (domnei(AT)aol.com)

Status

approved