A047873 a(n) = max_{r=1..n-1} ceiling(t(t(n)-t(r-1))/(n-r+1)), where t() = triangular numbers A000217.

1, 3, 8, 15, 27, 43, 65, 94, 130, 175, 229, 294, 369, 456, 557, 671, 800, 944, 1105, 1283, 1479, 1695, 1930, 2187, 2465, 2765, 3090, 3439, 3813, 4213, 4641, 5096, 5580, 6095, 6639, 7216, 7825, 8466, 9143, 9855

Offset

1,2

Comments

Another lower bound for Honaker triangle problem (A047837); conjectured to be exact value.

Links

Table of n, a(n) for n=1..40.

Formula

Empirical g.f.: -x*(x^15 - 3*x^14 + 3*x^13 - 5*x^12 + 5*x^11 - 9*x^10 + 7*x^9 - 10*x^8 + 7*x^7 - 9*x^6 + 5*x^5 - 6*x^4 + 2*x^3 - 3*x^2 - 1) / ((x-1)^4*(x^2-x+1)*(x^2+1)*(x^2+x+1)^2*(x^4-x^2+1)). [Colin Barker, Jan 18 2013]

Crossrefs

Cf. A047837, A047866.

Sequence in context: A081276 A210979 A047837 * A036419 A054107 A031125

Adjacent sequences: A047870 A047871 A047872 * A047874 A047875 A047876

Keyword

easy,nonn

Author

Mike Keith

Status

approved