This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A209105 #7 Jul 22 2025 21:38:45 %S A209105 122,34096,7154944,1404480904,272236743760,52675800891748, %T A209105 10191444894367900,1971869773009191300,381529277930963765396, %U A209105 73820911678439362478268,14283392072671820658161260 %N A209105 Number of 6Xn 0..2 arrays with new values 0..2 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors. %C A209105 Row 6 of A209100 %H A209105 R. H. Hardin, <a href="/A209105/b209105.txt">Table of n, a(n) for n = 1..210</a> %F A209105 Empirical: a(n) = 483*a(n-1) -93045*a(n-2) +9895994*a(n-3) -655000699*a(n-4) +28153218507*a(n-5) -771472287050*a(n-6) +11575521770914*a(n-7) -5333969777492*a(n-8) -3460511755733129*a(n-9) +60619944832280219*a(n-10) -122454879122841094*a(n-11) -9610060024477677636*a(n-12) +119490257201622127599*a(n-13) +207423246569123218904*a(n-14) -15418046735278157348540*a(n-15) +85958015930994934073828*a(n-16) +809517273485108604329443*a(n-17) -10872862333905128370604528*a(n-18) -553924361897541639230341*a(n-19) +628503974578083970787751095*a(n-20) -2441837003902470322705776546*a(n-21) -19135804539591412466515125841*a(n-22) +157196371353874391098869608556*a(n-23) +184930685928293621578721897714*a(n-24) -5212791777478985863598283828640*a(n-25) +8343380811716464763432941624104*a(n-26) +99943078075370200668702342185854*a(n-27) -385486750658814649071993027833855*a(n-28) -947326129545439583693615334446414*a(n-29) +7617076417557384976850188004727513*a(n-30) -1587365613230665275472648686777016*a(n-31) -81893089783126645169411368168862676*a(n-32) +154905729052219569334495329758007735*a(n-33) +392446436386226179411197434377941811*a(n-34) -1789366396909098001371959030444799187*a(n-35) +1364382304774676286186085515863856887*a(n-36) +7450756681407735007607770239017405077*a(n-37) -32742420723798992453476401619165532832*a(n-38) +34882707064638274850232798681677400146*a(n-39) +196690238938567903829556617524922100465*a(n-40) -642195656452343483207376794444201641353*a(n-41) -302741845834579655279069984112105879663*a(n-42) +3898930711936348369962805243570318234338*a(n-43) -2811628196998770649303159460561101126472*a(n-44) -12699154307737793869661985076853426155598*a(n-45) +20357131154883109280177933384191456925974*a(n-46) +20643883539066233274084030626803696790656*a(n-47) -64755513215769597861644458739579161901156*a(n-48) -928177211363479033745240114012556539704*a(n-49) +116393013534805718816923463675254988333020*a(n-50) -62922764613474031277505408520521940164664*a(n-51) -117636718952533538147029798845965591298928*a(n-52) +122662194993078191268927575331077554092224*a(n-53) +53377954500120792927391233551189754963712*a(n-54) -111660132397303689829356851421252048286208*a(n-55) +7919142148317395919389979426042637954304*a(n-56) +51518409827438947321954214341306278669824*a(n-57) -18670349951681657511291462879827883996160*a(n-58) -10933253490659848148544920316312898695168*a(n-59) +6995956832033163694328578109174268706816*a(n-60) +1686799976967671987881917375839533137920*a(n-61) -1253524043678855280232828496400957308928*a(n-62) -906202586627792174825114955918683930624*a(n-63) +309998526763988330640199202118903529472*a(n-64) +148552622821827192644092436874780475392*a(n-65) -20331273732734054176046805671907164160*a(n-66) +93663781756651920952176320882940051456*a(n-67) -77028642178807633010626944466396643328*a(n-68) +1689650677968769324222545429484535808*a(n-69) +8972893867255780734625567627712397312*a(n-70) -855929165188635245245315361739374592*a(n-71) -260331530489786581111126222776041472*a(n-72) for n>76 %e A209105 Some solutions for n=4 %e A209105 ..0..0..0..1....0..0..1..2....0..0..0..1....0..0..0..0....0..0..1..1 %e A209105 ..1..1..2..0....1..2..1..0....2..1..0..2....1..1..1..2....1..2..0..2 %e A209105 ..0..1..2..2....2..1..2..1....2..0..1..2....0..2..0..1....2..1..2..1 %e A209105 ..0..0..0..2....2..0..1..2....1..0..1..2....2..0..1..0....2..0..1..2 %e A209105 ..1..2..0..0....0..2..0..2....0..2..0..2....0..2..2..0....1..2..0..2 %e A209105 ..1..0..1..0....0..1..2..1....2..0..1..2....0..1..0..1....1..2..0..2 %K A209105 nonn %O A209105 1,1 %A A209105 _R. H. Hardin_ Mar 05 2012