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 A229929 #6 Jun 02 2025 08:39:46 %S A229929 3,115,1889,33119,575757,10015447,174306687,3033162257,52780116071, %T A229929 918441159087,15982039040815,278107289563015,4839412932483379, %U A229929 84211817278578727,1465390522949952937,25499620386183396001 %N A229929 Number of nX3 0..2 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value 2-x(i,j). %C A229929 Column 3 of A229934 %H A229929 R. H. Hardin, <a href="/A229929/b229929.txt">Table of n, a(n) for n = 1..210</a> %F A229929 Empirical: a(n) = 17*a(n-1) -35*a(n-2) +714*a(n-3) -186*a(n-4) +7255*a(n-5) +20662*a(n-6) -64966*a(n-7) +84269*a(n-8) +187347*a(n-9) -322147*a(n-10) -628502*a(n-11) -1841129*a(n-12) +1612168*a(n-13) +1569555*a(n-14) +6807437*a(n-15) +4484863*a(n-16) -10256653*a(n-17) -6172407*a(n-18) -30616026*a(n-19) +24692244*a(n-20) -26449944*a(n-21) +78202441*a(n-22) -22109082*a(n-23) +88650916*a(n-24) -93802931*a(n-25) +32432730*a(n-26) -90623604*a(n-27) +31406227*a(n-28) -43230346*a(n-29) +32065489*a(n-30) -12064122*a(n-31) +4898739*a(n-32) -6961489*a(n-33) -2339302*a(n-34) -1481520*a(n-35) -123582*a(n-36) +105456*a(n-37) +41286*a(n-38) -230321*a(n-39) +22096*a(n-40) -50268*a(n-41) -10864*a(n-42) -6264*a(n-43) -2368*a(n-44) +856*a(n-45) -680*a(n-46) +404*a(n-47) -32*a(n-48) -80*a(n-49) for n>50 %e A229929 Some solutions for n=3 %e A229929 ..1..0..2....0..2..0....0..1..1....2..0..0....2..0..1....1..1..1....2..0..2 %e A229929 ..1..0..0....0..1..0....2..2..2....0..2..1....0..1..0....0..2..1....2..2..1 %e A229929 ..1..1..2....2..1..2....0..2..0....2..0..1....1..2..2....0..0..1....0..2..1 %K A229929 nonn %O A229929 1,1 %A A229929 _R. H. Hardin_, Oct 04 2013