A217024 Number of city-block distance 1, pressure limit 2 movements in an nX4 array with each element moving exactly one horizontally or vertically and no element acquiring more than two neighbors

4, 1024, 108900, 12931216, 1501795009, 174892912804, 20353081850721, 2368756732515625, 275676538509042724, 32083375146710009409, 3733875752060633796100, 434549943674384511794401

Offset

1,1

Comments

Column 4 of A217028

Links

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

Formula

Empirical: a(n) = 138*a(n-1) -1763*a(n-2) -104096*a(n-3) +1809621*a(n-4) +15350519*a(n-5) -373958850*a(n-6) +742781203*a(n-7) +16974636444*a(n-8) -83414425341*a(n-9) -243838748413*a(n-10) +2303032008546*a(n-11) -642413643539*a(n-12) -27716237446800*a(n-13) +49075197330378*a(n-14) +144241631926804*a(n-15) -470008841261549*a(n-16) -140883178920985*a(n-17) +1769208519222178*a(n-18) -1130914844768352*a(n-19) -2544187846139448*a(n-20) +2892545854908279*a(n-21) +1630408747385312*a(n-22) -3021516801742966*a(n-23) -330376708494636*a(n-24) +1740628750155765*a(n-25) -171078581715509*a(n-26) -603090654119312*a(n-27) +132828725931224*a(n-28) +127444286159131*a(n-29) -39514256602536*a(n-30) -15636690313044*a(n-31) +6313677455724*a(n-32) +919389460803*a(n-33) -546250997674*a(n-34) -1662750703*a(n-35) +22252053530*a(n-36) -2029538078*a(n-37) -254802637*a(n-38) +44411642*a(n-39) -183141*a(n-40) -297102*a(n-41) +14334*a(n-42) +448*a(n-43) -49*a(n-44) +a(n-45)

Example

Some solutions for n=3 (movement: 0=n 1=e 2=s 3=w)
..2..1..3..3....1..3..2..3....1..2..1..2....2..2..1..3....1..3..2..3
..1..1..1..3....0..0..2..3....0..0..1..2....0..2..0..0....0..2..0..3
..1..0..3..0....0..1..1..0....0..0..1..3....1..3..1..3....0..3..1..3

Crossrefs

Sequence in context: A024059 A069920 A368371 * A013780 A139300 A004804

Adjacent sequences: A217021 A217022 A217023 * A217025 A217026 A217027

Keyword

nonn

Author

R. H. Hardin Sep 24 2012

Status

approved