login

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 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Number of length 6 nonnegative integer arrays starting and ending with 0 with adjacent elements unequal but differing by no more than n.
1

%I #8 Jun 11 2018 13:13:36

%S 0,24,138,454,1130,2370,4424,7588,12204,18660,27390,38874,53638,72254,

%T 95340,123560,157624,198288,246354,302670,368130,443674,530288,629004,

%U 740900,867100,1008774,1167138,1343454,1539030,1755220,1993424,2255088

%N Number of length 6 nonnegative integer arrays starting and ending with 0 with adjacent elements unequal but differing by no more than n.

%C Row 5 of A205341.

%H R. H. Hardin, <a href="/A205343/b205343.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = (23/12)*n^4 - (1/2)*n^3 + (1/12)*n^2 - (3/2)*n.

%F Conjectures from _Colin Barker_, Jun 11 2018: (Start)

%F G.f.: 2*x^2*(12 + 9*x + 2*x^2) / (1 - x)^5.

%F a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.

%F (End)

%e Some solutions for n=5:

%e ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

%e ..5....4....3....4....2....4....3....5....5....3....5....4....5....1....1....1

%e ..1....2....2....9....5....7....6....6....2....6....0....2....2....0....6....5

%e ..5....0....5....8....1....3....7....8....6....4....5....0....1....2....9....9

%e ..3....4....1....5....5....1....2....4....2....5....2....1....5....1....5....4

%e ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

%Y Cf. A205341.

%K nonn

%O 1,2

%A _R. H. Hardin_, Jan 26 2012