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

1,2

Links

Michael S. Branicky, Table of n, a(n) for n = 1..101

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

Prog

(PARI) ss(n)=sum(i=1, n, (i+1)/i); for (i=1, 1000, if(isprime(numerator(ss(i))), print1(i, ", ")))

Crossrefs

Cf. A091815, A166939.

Sequence in context: A091415 A166342 A361502 * A266400 A274914 A100993

Adjacent sequences: A091813 A091814 A091815 * A091817 A091818 A091819

Keyword

nonn

Author

Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 07 2004

Extensions

a(30) and beyond from Michael S. Branicky, Aug 26 2024

Status

approved