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 A056141 #14 Mar 22 2020 04:01:59 %S A056141 -1,0,4,0,-6,0,0,0,30,0,-18,0,0,0,42,0,-30,0,0,0,-22,0,0,0,0,0,128,0, %T A056141 -112,0,0,0,0,0,98,0,0,0,90,0,-78,0,0,0,-70,0,0,0,0,0,36,0,0,0,0,0, %U A056141 248,0,-232,0,0,0,0,0,158,0,0,0,150,0,-280,0,0,0,0,0,182 %N A056141 a(n) = primefloor(n)*primeceiling(n) - previousprime(n)*nextprime(n). %F A056141 a(n) = A007917(n)*A007918(n) - A007917(n-1)*A007918(n+1). %F A056141 a(n) = A030664(n) - A013638(n). %F A056141 a(n) = A056140(n) - A056139(n). %F A056141 a(n) = A056140(n) if n is prime, a(n)=0 otherwise. %e A056141 a(3)=3*3-2*5=-1, a(4)=3*5-3*5=0 %o A056141 (PARI) a(n) = if (isprime(n), n^2 - precprime(n-1)*nextprime(n+1), 0); \\ _Michel Marcus_, Mar 22 2020 %Y A056141 Cf. A056139, A056140. %Y A056141 Cf. A056221 (nonzero terms). %K A056141 easy,sign %O A056141 3,3 %A A056141 _Henry Bottomley_, Jun 15 2000 %E A056141 More terms from _Michel Marcus_, Mar 22 2020