A269652 Number of length-n 0..4 arrays with no adjacent pair x,x+1 repeated.

5, 25, 125, 621, 3065, 15036, 73348, 355921, 1718569, 8259567, 39522507, 188338770, 894017122, 4228223130, 19928007170, 93614937601, 438406639797, 2047055696994, 9531639358730, 44264054228691, 205038988521635, 947492030288164

Offset

1,1

Comments

Column 4 of A269656.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 25*a(n-1) -270*a(n-2) +1665*a(n-3) -6595*a(n-4) +18220*a(n-5) -38090*a(n-6) +64915*a(n-7) -94320*a(n-8) +119745*a(n-9) -134854*a(n-10) +136350*a(n-11) -124755*a(n-12) +103755*a(n-13) -78640*a(n-14) +54403*a(n-15) -34320*a(n-16) +19685*a(n-17) -10220*a(n-18) +4770*a(n-19) -1977*a(n-20) +715*a(n-21) -220*a(n-22) +55*a(n-23) -10*a(n-24) +a(n-25)

Example

Some solutions for n=7
..4. .3. .4. .2. .1. .3. .1. .3. .1. .0. .0. .2. .3. .2. .4. .1
..0. .3. .4. .4. .1. .4. .3. .4. .1. .3. .3. .3. .3. .1. .4. .2
..4. .2. .0. .2. .2. .0. .4. .0. .4. .0. .0. .4. .0. .2. .2. .3
..2. .0. .3. .1. .2. .0. .4. .2. .1. .1. .3. .2. .0. .3. .4. .3
..4. .0. .0. .0. .1. .3. .4. .1. .3. .3. .0. .1. .3. .0. .4. .3
..1. .2. .1. .2. .3. .2. .2. .4. .1. .4. .2. .4. .1. .4. .0. .4
..4. .1. .3. .4. .2. .1. .0. .4. .4. .3. .4. .2. .3. .4. .2. .4

Crossrefs

Cf. A269656.

Sequence in context: A269490 A370144 A269772 * A163844 A250357 A216125

Adjacent sequences: A269649 A269650 A269651 * A269653 A269654 A269655

Keyword

nonn

Author

R. H. Hardin, Mar 02 2016

Status

approved