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 A286714 #11 Sep 11 2019 15:50:55 %S A286714 -1,0,0,2,4,4,12,0,8,16,20,32,40,8,24,40,32,60,4,24,60,84,24,56,24, %T A286714 136,104,36,44,116,184,48,84,184,68,252,72,280,68,144,56,292,140,192, %U A286714 120,338,276,120,144,262,192,376,120,268,192,236,64,168,240,492,348,388 %N A286714 Difference phi(p-1) - phi(p+1) for lesser of twin primes. %H A286714 Amiram Eldar, <a href="/A286714/b286714.txt">Table of n, a(n) for n = 1..10000</a> %H A286714 Stephan Ramon Garcia, Elvis Kahoro, Florian Luca, <a href="https://arxiv.org/abs/1705.02485">Primitive root discrepancy for twin primes</a>, arXiv:1705.02485 [math.NT], 2017. %t A286714 (EulerPhi[#-1] - EulerPhi[#+1]) &@ Select[Prime@ Range@ 310, PrimeQ[# + 2] &] (* _Giovanni Resta_, May 13 2017 *) %o A286714 (PARI) lista(nn) = forprime(p=2, nn, if (isprime(p+2), print1(eulerphi(p-1)-eulerphi(p+1), ", "))); %Y A286714 Cf. A001359, A006512, A008330, A286715. %K A286714 sign %O A286714 1,4 %A A286714 _Michel Marcus_, May 13 2017