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 A087611 #19 Feb 03 2023 08:16:45 %S A087611 0,0,1,2,0,0,2,2,4,8,8,0,1,0,1,4,7,6,9,10,9,12,13,16,21,22,21,22,21, %T A087611 22,2,2,4,2,8,6,8,10,10,12,14,12,18,16,16,14,22,30,30,28,28,30,28,34, %U A087611 36,38,40,38,40,40,38,44,54,54,52,52,62,64,1,68,68,70,1,2,3,2,3,6,5,8 %N A087611 a(n) = (prime(n) - 1) mod n. %o A087611 (Magma) [((NthPrime(n) -1) mod n): n in [1..100]]; // _Vincenzo Librandi_, Apr 06 2011 %o A087611 (PARI) a(n) = (prime(n)-1) % n; \\ _Kevin Ryde_, Feb 03 2023 %Y A087611 Cf. A023143 (indices of 0's). %Y A087611 Cf. A006093, A004648. %K A087611 nonn,easy %O A087611 1,4 %A A087611 _Reinhard Zumkeller_, Sep 11 2003