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 A223809 #6 Jul 23 2025 04:33:02 %S A223809 296,87616,8165133,342521725,8597979566,151474085262,2058985931297, %T A223809 22901512677629,216485354275124,1784167200609912,13053474850518508, %U A223809 85927775923343738,514305111112459789,2823064297778339125 %N A223809 Number of nX5 0..3 arrays with rows, columns, diagonals and antidiagonals unimodal. %C A223809 Column 5 of A223811 %H A223809 R. H. Hardin, <a href="/A223809/b223809.txt">Table of n, a(n) for n = 1..55</a> %F A223809 Empirical: a(n) = (12185409283/15043832793341144432640000000)*n^30 + (65289291955553/4420880996869850977271808000000)*n^29 + (21718473047041/19884022474676990902272000000)*n^28 + (2120108278451/127355198250507042816000000)*n^27 + (15561105953549293/36296231501394507202560000000)*n^26 + (289358623979/26564081706860544000000)*n^25 + (46195046293174813/2345294958551645080780800000)*n^24 + (2895943411744833937/781764986183881693593600000)*n^23 - (1934558843887147381/509846730119922843648000000)*n^22 + (48760416035116711/147141913454523187200000)*n^21 + (21826875298852452953/4855683143999265177600000)*n^20 - (156850672232660797/13601353344535756800000)*n^19 - (81113944137104012165989/348842499555736682496000000)*n^18 + (24830083604445741151639/930246665481964486656000)*n^17 - (2812142506870759694352953/4104029406538078617600000)*n^16 + (97155764191026540631493/5922120355754803200000)*n^15 - (6012916017623459423535490877/16611547597892222976000000)*n^14 + (42676596532256238158237909/6084815969923891200000)*n^13 - (451076788569987755746145023843/4025105764104654028800000)*n^12 + (1675232798260911600311989982501/1158742568454370099200000)*n^11 - (7157215149697402554044186072517719/477981309487427665920000000)*n^10 + (552107030494681804261361610031/4436844978069504000000)*n^9 - (2415940983456589943036911811427841/2908351883124559872000000)*n^8 + (103326033975482855639269665005533/23082157802575872000000)*n^7 - (7877089396965831951756259428407549/399547133702196480000000)*n^6 + (10172973554483534081526630673099/140642547829056000000)*n^5 - (34242481981306851689859252316747/153159734585841984000)*n^4 + (27230471296744908127446139183/47668762709568000)*n^3 - (2769560342993078431580752847/2411812398996000)*n^2 + (18165979496961348183233/10782822050)*n - 1410583198450 for n>15 %e A223809 Some solutions for n=3 %e A223809 ..0..0..0..0..0....0..0..0..1..0....0..0..0..0..3....0..0..2..2..1 %e A223809 ..0..2..1..1..1....0..0..3..3..0....0..0..0..3..2....0..0..3..2..1 %e A223809 ..0..0..0..1..0....0..2..2..2..2....0..0..3..2..1....0..0..2..2..2 %K A223809 nonn %O A223809 1,1 %A A223809 _R. H. Hardin_ Mar 27 2013