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!)
 A200053 Number of -4..4 arrays X (0..n-1) of n elements with zero sum and elements alternately strictly increasing and strictly decreasing. 1
 1, 8, 36, 172, 840, 4172, 20978, 106674, 545698, 2811236, 14534258, 75522854, 393338058, 2056376914, 10767639532, 56550307652, 297322835298, 1567022163228, 8265441146830, 43685281805084, 231022736833454, 1223830782531260 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 4 of A200057. LINKS R. H. Hardin, Table of n, a(n) for n = 1..200 EXAMPLE Some solutions for n=6: .-2....2...-1...-3...-2....4....0...-1....0....2...-4....2...-1....0....0....1 ..2...-3....4....1....2....0....4....3...-2....0....2....4....2....4....2....0 ..1....2...-3....0...-1....3...-3...-1....4....2...-1....0...-3...-2...-2....2 ..4...-1....0....4....0...-3....3....4...-4...-3....1....1....1....1....1...-4 .-3....1...-2...-3...-3....0...-3...-3....2....1...-2...-4....0...-2...-3....4 .-2...-1....2....1....4...-4...-1...-2....0...-2....4...-3....1...-1....2...-3 MAPLE T:= proc(a, n, s)    option remember;    if n = 1 then       if s = a then 1       else 0       fi    else      add(procname(-j, n-1, a-s), j=a+1..4)    fi end proc: A:= proc(n)  2*add(T(a, n, 0), a=-4..4) end proc: A(1):= 1: seq(A(n), n=1..30); # Robert Israel, Nov 19 2014 CROSSREFS Cf. A200057. Sequence in context: A207099 A055064 A014347 * A164545 A199310 A316107 Adjacent sequences:  A200050 A200051 A200052 * A200054 A200055 A200056 KEYWORD nonn AUTHOR R. H. Hardin, Nov 13 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 6 09:43 EST 2021. Contains 349563 sequences. (Running on oeis4.)