A250097 Denominator of the harmonic mean of the prime factors, without multiplicity, of n.

1, 1, 1, 1, 5, 1, 1, 1, 7, 1, 5, 1, 9, 4, 1, 1, 5, 1, 7, 5, 13, 1, 5, 1, 15, 1, 9, 1, 31, 1, 1, 7, 19, 6, 5, 1, 21, 8, 7, 1, 41, 1, 13, 4, 25, 1, 5, 1, 7, 10, 15, 1, 5, 8, 9, 11, 31, 1, 31, 1, 33, 5, 1, 9, 61, 1, 19, 13, 59, 1, 5, 1, 39, 4, 21, 9, 71, 1, 7

Offset

2,5

Links

Colin Barker, Table of n, a(n) for n = 2..1000

Example

a(6) = 5 because the distinct prime factors of 6 are [2,3] and 2 / (1/2+1/3) = 12/5.

Prog

(PARI)
harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])
a(n) = denominator(harmonicmean(factorint(n)~[1, ]))
vector(100, n, a(n+1))

Crossrefs

Cf. A250096.

Sequence in context: A284254 A309206 A358016 * A340678 A028235 A028236

Adjacent sequences: A250094 A250095 A250096 * A250098 A250099 A250100

Keyword

nonn

Author

Colin Barker, Nov 12 2014

Status

approved