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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A189809 Number of right triangles on an (n+1) X 5 grid. 1
 46, 158, 342, 596, 926, 1308, 1754, 2250, 2794, 3390, 4026, 4702, 5426, 6190, 6994, 7838, 8726, 9654, 10622, 11630, 12678, 13766, 14894, 16062, 17270, 18518, 19806, 21134, 22502, 23910, 25358, 26846, 28374, 29942, 31550, 33198, 34886, 36614, 38382 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 4 of A189814. LINKS R. H. Hardin, Table of n, a(n) for n = 1..200 FORMULA Empirical: a(n) = 20*n^2 + 228*n - 930 for n>15. Conjectures from Colin Barker, May 03 2018: (Start) G.f.: 2*x*(23 + 10*x + 3*x^2 - x^3 + 3*x^4 - 12*x^5 + 6*x^6 - 7*x^7 - x^8 + 2*x^9 - 6*x^10 + 4*x^12 - 4*x^13 + 2*x^16 - 2*x^17) / (1 - x)^3. a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>11. (End) EXAMPLE Some solutions for n=3: ..1..4....3..3....3..3....3..3....1..2....2..0....3..2....0..3....3..2....0..1 ..0..4....0..3....1..3....1..1....2..1....0..1....0..2....0..2....2..2....0..0 ..1..0....3..4....3..0....2..4....3..4....3..2....3..3....1..3....3..3....3..1 CROSSREFS Cf. A189814. Sequence in context: A044378 A044759 A223607 * A251467 A251460 A235767 Adjacent sequences:  A189806 A189807 A189808 * A189810 A189811 A189812 KEYWORD nonn AUTHOR R. H. Hardin, Apr 28 2011 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 December 8 00:04 EST 2021. Contains 349590 sequences. (Running on oeis4.)