A083275 a(n) = smallest number not occurring earlier such that a(1)*a(2)*...*a(n) - 1 is prime.
3, 1, 2, 4, 7, 5, 6, 11, 12, 10, 13, 17, 14, 16, 15, 8, 18, 23, 21, 26, 22, 27, 41, 30, 20, 57, 32, 29, 24, 65, 42, 38, 28, 63, 35, 19, 58, 31, 36, 61, 45, 37, 33, 69, 53, 67, 127, 40, 95, 25, 86, 48, 39, 72, 70, 79, 54, 74, 91, 125, 85, 94, 46, 9, 80, 60, 119, 167, 139, 90, 49
Offset: 1
Keywords
Links
- Alois P. Heinz and Giovanni Resta, Table of n, a(n) for n = 1..1200 (first 300 terms from Alois P. Heinz)
Programs
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Maple
b:= proc() false end: m:= proc(n) option remember; a(n)*m(n-1) end: m(0):=1: a:= proc(n) option remember; local k; for k while b(k) or not isprime(k*m(n-1)-1) do od; b(k):=true; k end: seq(a(n), n=1..80); # Alois P. Heinz, Jun 17 2015 -
Mathematica
p=1; L={}; Do[k=1; While[ MemberQ[L, k] || !PrimeQ[p*k - 1], k++]; p *= k; AppendTo[L, k], {30}]; L (* Giovanni Resta, Jun 23 2015 *) -
PARI
v=[3];n=1;while(n<100,s=-1+n*prod(i=1,#v,v[i]);if(isprime(s)&&!vecsearch(vecsort(v),n),v=concat(v,n);n=0);n++);v \\ Derek Orr, Jun 16 2015
Extensions
Name corrected by Derek Orr, Jun 16 2015