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A340649 a(n) = (n*prime(n+1)) mod prime(n).

%I A340649 #34 Sep 08 2022 08:46:26
%S A340649 1,1,1,2,10,11,14,13,8,20,4,11,26,13,43,43,34,47,9,40,53,9,55,14,3,52,
%T A340649 5,56,7,81,124,61,66,62,70,65,65,152,67,67,82,58,86,176,90,154,142,
%U A340649 192,98,200,73,104,48,73,73,73,114,77,236,120,44,282,252,128
%N A340649 a(n) = (n*prime(n+1)) mod prime(n).
%H A340649 Seiichi Manyama, <a href="/A340649/b340649.txt">Table of n, a(n) for n = 1..10000</a>
%H A340649 Simon Strandgaard, <a href="https://youtu.be/jy4DimtndFA">Animations of ((n+k)*prime(n+1)) mod prime(n) when k varies</a>, YouTube video, 2021.
%F A340649 a(n) = A117495(n+1) mod prime(n). - _Michel Marcus_, Jan 15 2021
%e A340649 a(1) = (prime(1+1) * 1) mod prime(1) =  3 * 1 mod  2 = 1,
%e A340649 a(2) = (prime(2+1) * 2) mod prime(2) =  5 * 2 mod  3 = 1,
%e A340649 a(3) = (prime(3+1) * 3) mod prime(3) =  7 * 3 mod  5 = 1,
%e A340649 a(4) = (prime(4+1) * 4) mod prime(4) = 11 * 4 mod  7 = 2,
%e A340649 a(5) = (prime(5+1) * 5) mod prime(5) = 13 * 5 mod 11 = 10.
%t A340649 Table[Mod[Prime[n + 1]*n, Prime[n]],{n, 1, 64}] (* _Robert P. P. McKone_, Jan 15 2021 *)
%o A340649 (Ruby) require 'prime'
%o A340649 values = []
%o A340649 primes = Prime.first(20)
%o A340649 primes.each_index do |n|
%o A340649     next if n < 1
%o A340649     values << (primes[n] * n) % primes[n-1]
%o A340649 end
%o A340649 p values
%o A340649 (PARI) a(n) = prime(n+1)*n % prime(n); \\ _Michel Marcus_, Jan 15 2021
%o A340649 (Magma) [ (n*NthPrime(n+1)) mod NthPrime(n) : n in [1..60]]; // _Wesley Ivan Hurt_, Apr 23 2021
%Y A340649 Cf. A000040, A117495, A340128.
%K A340649 nonn,look
%O A340649 1,4
%A A340649 _Simon Strandgaard_, Jan 14 2021