A091816 Numbers m such that the numerator of Sum_{i=1..m} (i+1)/i is prime.
1, 2, 3, 4, 8, 14, 15, 17, 19, 21, 22, 27, 28, 31, 55, 59, 80, 108, 114, 126, 199, 225, 248, 316, 352, 406, 467, 601, 875, 1016, 1040, 1056, 1095, 1245, 1252, 1418, 1468, 1471, 1496, 1627, 1724, 1728, 1873, 1892, 2015, 2039, 2684, 2971, 3043, 3165, 3226, 3368, 3429
Offset: 1
Keywords
Links
- Michael S. Branicky, Table of n, a(n) for n = 1..101
Programs
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Maple
f:= proc(n) option remember; `if`(n<1, 0, f(n-1)+(n+1)/n) end: q:= n-> isprime(numer(f(n))): select(q, [$1..2000])[]; # Alois P. Heinz, Aug 27 2024
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PARI
ss(n)=sum(i=1,n,(i+1)/i); for (i=1,1000,if(isprime(numerator(ss(i))),print1(i,",")))
Extensions
a(30) and beyond from Michael S. Branicky, Aug 26 2024