A210781 Number of nX1 1..4 arrays with no element with value z exactly a city block distance of z from another element with value z

4, 15, 53, 170, 497, 1407, 3962, 10867, 30956, 87542, 248218, 711766, 2029175, 5781750, 16430665, 46462998, 131837484, 374313604, 1064195679, 3028749764, 8608397556, 24458778262, 69472002871, 197274426596, 560475590510

Offset

1,1

Comments

Column 1 of A210788

Links

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

Formula

Empirical: a(n) = a(n-2) +2*a(n-3) +4*a(n-4) +38*a(n-5) +106*a(n-6) +172*a(n-7) +596*a(n-8) +573*a(n-9) +971*a(n-10) +744*a(n-11) -1425*a(n-12) -4335*a(n-13) -10525*a(n-14) -11517*a(n-15) -13462*a(n-16) -6001*a(n-17) -4772*a(n-18) +619*a(n-19) +10548*a(n-20) +45667*a(n-21) +64053*a(n-22) +34800*a(n-23) -11095*a(n-24) -26829*a(n-25) +41629*a(n-26) +81493*a(n-27) -35792*a(n-28) -237880*a(n-29) -186310*a(n-30) +61561*a(n-31) +67920*a(n-32) -147561*a(n-33) -221267*a(n-34) -90437*a(n-35) -13145*a(n-36) +33145*a(n-37) +101632*a(n-38) +63235*a(n-39) +3056*a(n-40) -2932*a(n-41) -6086*a(n-42) -5505*a(n-43) +115*a(n-44) +649*a(n-45) +319*a(n-46) +258*a(n-47) +4*a(n-48) -24*a(n-49) for n>51

Example

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

Crossrefs

Sequence in context: A230623 A162978 A171309 * A367818 A303271 A289802

Adjacent sequences: A210778 A210779 A210780 * A210782 A210783 A210784

Keyword

nonn

Author

R. H. Hardin Mar 26 2012

Status

approved