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 A254221 #6 Jul 23 2025 14:33:29 %S A254221 0,2,4,22,24,96,168,388,490,1024,1168,2138,3000,4554,5084,7872,8570, %T A254221 12358,15532,20538,22120,30338,35972,45928,54068,66830,71348,90658, %U A254221 95374,115162,132074,156726,177542,212556,221796,258292,289706,334554,349466 %N A254221 Number of length 4 1..(n+2) arrays with no leading or trailing partial sum equal to a prime and no consecutive values equal. %C A254221 Row 4 of A254218 %H A254221 R. H. Hardin, <a href="/A254221/b254221.txt">Table of n, a(n) for n = 1..210</a> %e A254221 Some solutions for n=4 %e A254221 ..6....6....1....4....4....4....4....6....1....6....1....1....1....4....6....4 %e A254221 ..4....2....5....6....2....6....6....4....3....4....5....5....3....2....3....2 %e A254221 ..5....6....3....2....4....2....4....2....2....6....3....4....5....3....5....6 %e A254221 ..1....4....1....4....6....6....6....4....4....4....6....6....1....1....4....4 %K A254221 nonn %O A254221 1,2 %A A254221 _R. H. Hardin_, Jan 26 2015