This site is supported by donations to The OEIS Foundation.

 Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A201975 Number of n X 2 0..3 arrays with rows and columns lexicographically nondecreasing read forwards and nonincreasing read backwards. 1
 4, 30, 72, 131, 208, 304, 420, 557, 716, 898, 1104, 1335, 1592, 1876, 2188, 2529, 2900, 3302, 3736, 4203, 4704, 5240, 5812, 6421, 7068, 7754, 8480, 9247, 10056, 10908, 11804, 12745, 13732, 14766, 15848, 16979, 18160, 19392, 20676, 22013, 23404, 24850 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 2 of A201981. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = (1/6)*n^3 + 7*n^2 + (23/6)*n - 7. Conjectures from Colin Barker, May 25 2018: (Start) G.f.: x*(4 + 14*x - 24*x^2 + 7*x^3) / (1 - x)^4. a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4. (End) EXAMPLE Some solutions for n=9. ..0..3....1..3....0..3....0..3....1..3....0..3....0..3....1..2....0..3....0..1 ..0..3....1..3....0..3....0..3....2..2....0..3....1..2....3..1....0..3....3..0 ..1..2....1..3....0..3....0..3....2..2....0..3....1..2....3..1....1..2....3..0 ..1..2....1..3....0..3....0..3....2..2....0..3....1..2....3..1....2..1....3..0 ..1..2....1..3....2..0....0..3....2..2....2..1....1..2....3..1....2..1....3..0 ..2..0....1..3....2..0....1..2....2..2....2..1....1..2....3..1....2..1....3..0 ..2..0....2..2....2..0....1..2....2..2....2..1....1..2....3..1....3..0....3..0 ..2..0....3..1....2..0....1..2....3..0....2..1....3..1....3..1....3..0....3..0 ..2..0....3..1....2..0....2..1....3..0....2..1....3..1....3..1....3..0....3..0 CROSSREFS Cf. A201981. Sequence in context: A268037 A248528 A296247 * A109670 A014697 A211624 Adjacent sequences:  A201972 A201973 A201974 * A201976 A201977 A201978 KEYWORD nonn AUTHOR R. H. Hardin, Dec 07 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 14 23:10 EST 2018. Contains 318141 sequences. (Running on oeis4.)