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 A269431 Number of length-n 0..4 arrays with no repeated value greater than the previous repeated value. 1

%I #9 Jan 21 2019 12:32:28

%S 5,25,125,615,2995,14455,69235,329430,1558430,7334806,34364270,

%T 160340610,745362730,3453222850,15949215754,73454841775,337413819915,

%U 1546145183895,7068979186035,32251365241137,146853223312325,667445619383425

%N Number of length-n 0..4 arrays with no repeated value greater than the previous repeated value.

%H R. H. Hardin, <a href="/A269431/b269431.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 20*a(n-1) - 155*a(n-2) + 560*a(n-3) - 810*a(n-4) - 136*a(n-5) + 810*a(n-6) + 560*a(n-7) + 155*a(n-8) + 20*a(n-9) + a(n-10).

%F Empirical g.f.: x*(5 - 75*x + 400*x^2 - 810*x^3 + 120*x^4 + 810*x^5 + 560*x^6 + 155*x^7 + 20*x^8 + x^9) / (1 - 4*x - x^2)^5. - _Colin Barker_, Jan 21 2019

%e Some solutions for n=7:

%e ..3. .2. .3. .4. .2. .3. .1. .1. .1. .3. .0. .2. .0. .0. .0. .0

%e ..1. .1. .3. .1. .1. .2. .2. .3. .3. .2. .0. .2. .1. .1. .0. .3

%e ..4. .3. .4. .1. .0. .0. .2. .3. .1. .0. .2. .0. .4. .0. .0. .4

%e ..1. .2. .2. .0. .2. .2. .0. .4. .0. .0. .4. .4. .2. .2. .2. .4

%e ..1. .2. .1. .1. .2. .1. .4. .0. .2. .0. .0. .1. .4. .4. .1. .2

%e ..0. .4. .4. .1. .4. .0. .0. .3. .4. .1. .2. .2. .0. .3. .0. .4

%e ..4. .3. .3. .4. .3. .4. .2. .0. .2. .2. .1. .4. .4. .2. .4. .0

%Y Column 4 of A269435.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 26 2016

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Last modified February 23 11:40 EST 2024. Contains 370283 sequences. (Running on oeis4.)