The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A271035 Number of 3 X 3 X 3 triangular 0..n arrays with some element less than a w, nw or ne neighbor exactly once. 1
 10, 72, 294, 896, 2268, 5040, 10164, 19008, 33462, 56056, 90090, 139776, 210392, 308448, 441864, 620160, 854658, 1158696, 1547854, 2040192, 2656500, 3420560, 4359420, 5503680, 6887790, 8550360, 10534482, 12888064, 15664176, 18921408 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = (1/60)*n^6 + (7/30)*n^5 + (5/4)*n^4 + (19/6)*n^3 + (56/15)*n^2 + (8/5)*n. Conjectures from Colin Barker, Jan 30 2019: (Start) G.f.: 2*x*(5 + x) / (1 - x)^7. a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7. (End) EXAMPLE Some solutions for n=4: ....1......4......0......3......0......0......0......1......3......1......0 ...0.1....2.4....2.4....0.4....2.1....0.0....0.0....0.2....0.3....1.1....2.2 ..3.3.3..4.4.4..1.4.4..3.4.4..2.2.2..2.2.1..2.3.0..1.3.4..3.3.3..0.2.2..4.2.2 CROSSREFS Row 3 of A271034. Sequence in context: A221548 A037579 A166791 * A108276 A264159 A228316 Adjacent sequences:  A271032 A271033 A271034 * A271036 A271037 A271038 KEYWORD nonn AUTHOR R. H. Hardin, Mar 29 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 18 03:14 EDT 2021. Contains 343072 sequences. (Running on oeis4.)