A340128 a(n) = (n*prime(n)) mod prime(n+1).

2, 1, 1, 6, 3, 10, 5, 14, 4, 11, 8, 34, 17, 38, 16, 22, 27, 26, 66, 33, 32, 78, 40, 2, 1, 51, 106, 53, 110, 88, 7, 82, 73, 107, 81, 98, 104, 15, 112, 118, 99, 153, 107, 21, 109, 81, 105, 35, 131, 33, 172, 137, 223, 190, 196, 202, 157, 206, 45, 163, 269, 53

Offset: 1

Author

Simon Strandgaard, Jan 15 2021

Keywords

• nonn
• look

Examples

			a(1) = (prime(1) * 1) mod prime(1+1) =  2 * 1 mod  3 = 2,
a(2) = (prime(2) * 2) mod prime(2+1) =  3 * 2 mod  5 = 1,
a(3) = (prime(3) * 3) mod prime(3+1) =  5 * 3 mod  7 = 1,
a(4) = (prime(4) * 4) mod prime(4+1) =  7 * 4 mod 11 = 6,
a(5) = (prime(5) * 5) mod prime(5+1) = 11 * 5 mod 13 = 3.
		

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A033286, A340649.

Programs

Mathematica

Table[Mod[n*Prime[n],Prime[n+1]],{n,62}] (* Stefano Spezia, Jan 17 2021 *)

PARI

a(n) = (prime(n)*n) % prime(n+1); \\ Michel Marcus, Jan 20 2021

Ruby

require 'prime'
values = []
primes = Prime.first(20)
primes.each_index do |n|
    next if n < 1
    values << (primes[n-1] * n) % primes[n]
end
p values