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 A212784 #8 Jul 22 2025 22:57:34 %S A212784 8,66,350,1134,3010,6724,13544,24870,42952,70060,109638,165098,241342, %T A212784 343074,476992,649304,868684,1143156,1483630,1900056,2405958,3013428, %U A212784 3738744,4596484,5605944,6784266,8154174,9735586,11554762,13634780 %N A212784 Half the number of 0..n arrays of length 5 with second differences nonzero. %C A212784 Row 3 of A212782 %H A212784 R. H. Hardin, <a href="/A212784/b212784.txt">Table of n, a(n) for n = 1..210</a> %F A212784 Empirical: a(n) = a(n-1) +2*a(n-2) -2*a(n-4) -4*a(n-5) +a(n-6) +3*a(n-7) +3*a(n-8) +a(n-9) -4*a(n-10) -2*a(n-11) +2*a(n-13) +a(n-14) -a(n-15) %e A212784 Some solutions for n=5 %e A212784 ..4....0....0....5....0....3....0....5....1....2....1....2....2....2....2....0 %e A212784 ..2....1....2....5....3....2....3....1....3....2....0....3....4....5....5....5 %e A212784 ..1....1....2....1....2....4....4....2....2....5....2....1....2....3....0....5 %e A212784 ..5....2....3....4....2....3....2....5....0....1....0....5....1....0....0....0 %e A212784 ..1....0....3....3....4....4....1....1....3....4....0....4....1....4....5....3 %K A212784 nonn %O A212784 1,1 %A A212784 _R. H. Hardin_ May 27 2012