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 A223666 #6 Jul 23 2025 04:22:03 %S A223666 16,256,2527,18980,136289,1023339,8052573,64796052,523162622, %T A223666 4210122961,33781534586,270773273163,2170507336531,17404421705191, %U A223666 139588544598990,1119608454999432,8980016929917601,72024132676487746,577661751732689211 %N A223666 Number of nX5 0..1 arrays with rows, diagonals and antidiagonals unimodal. %C A223666 Column 5 of A223669 %H A223666 R. H. Hardin, <a href="/A223666/b223666.txt">Table of n, a(n) for n = 1..210</a> %F A223666 Empirical: a(n) = 14*a(n-1) -52*a(n-2) +2*a(n-3) +197*a(n-4) +854*a(n-5) -1805*a(n-6) -26237*a(n-7) +86043*a(n-8) -70614*a(n-9) +170464*a(n-10) +399202*a(n-11) -2739146*a(n-12) +4095044*a(n-13) -10039780*a(n-14) +2577182*a(n-15) +24545705*a(n-16) -54040002*a(n-17) +167369490*a(n-18) -85060776*a(n-19) -28060708*a(n-20) -389208891*a(n-21) +459909922*a(n-22) +2683456378*a(n-23) -4388644180*a(n-24) -5542051151*a(n-25) -2414407341*a(n-26) +32349457536*a(n-27) +12515704412*a(n-28) -98186425408*a(n-29) -47665614177*a(n-30) +197523619448*a(n-31) +269900883869*a(n-32) -475417489889*a(n-33) -557567876049*a(n-34) +781710113042*a(n-35) +1046331021897*a(n-36) -847156975368*a(n-37) -2150199310855*a(n-38) +1141102444689*a(n-39) +2763026992524*a(n-40) -1108892309385*a(n-41) -3095005070434*a(n-42) +372805026225*a(n-43) +3825246453473*a(n-44) -381900163490*a(n-45) -3024861283470*a(n-46) +239728926637*a(n-47) +2504270286051*a(n-48) +252573497058*a(n-49) -2433283268771*a(n-50) -401711721919*a(n-51) +374998537102*a(n-52) +1383132583853*a(n-53) -540047390184*a(n-54) +123349296118*a(n-55) +364680760759*a(n-56) -406537833072*a(n-57) +329370465626*a(n-58) -927362054456*a(n-59) +96704047076*a(n-60) -90681009763*a(n-61) +444716709062*a(n-62) +392499685319*a(n-63) -228651167608*a(n-64) -64865394701*a(n-65) -27260982030*a(n-66) -5237026151*a(n-67) +5531571132*a(n-68) -124945968364*a(n-69) +62262537257*a(n-70) +50291998098*a(n-71) -17594004031*a(n-72) -1497064747*a(n-73) -14021053454*a(n-74) +17588728808*a(n-75) -464880468*a(n-76) -4736625394*a(n-77) -1543338426*a(n-78) +962821324*a(n-79) +1113573248*a(n-80) -451839972*a(n-81) -202718964*a(n-82) +36440824*a(n-83) +88759936*a(n-84) -3568528*a(n-85) -21856096*a(n-86) -1651968*a(n-87) +2626688*a(n-88) +1258624*a(n-89) -261376*a(n-90) -184320*a(n-91) +14336*a(n-92) +8192*a(n-93) %e A223666 Some solutions for n=4 %e A223666 ..1..1..1..1..0....0..0..1..1..1....1..1..1..1..1....1..1..1..0..0 %e A223666 ..0..1..1..1..1....1..1..1..1..1....0..1..1..1..1....0..1..0..0..0 %e A223666 ..1..1..1..1..0....0..1..1..1..1....0..1..1..0..0....1..1..1..0..0 %e A223666 ..0..1..1..0..0....1..1..1..0..0....1..0..0..0..0....0..0..1..0..0 %K A223666 nonn %O A223666 1,1 %A A223666 _R. H. Hardin_ Mar 25 2013