OFFSET
1,2
LINKS
Colin Barker, Table of n, a(n) for n = 1..850
EXAMPLE
a(3) = 151 because the first 3 heptagonal numbers are [1,7,18], and 3/(1/1+1/7+1/18) = 378/151.
PROG
(PARI)
harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])
s=vector(30); for(n=1, #s, s[n]=denominator(harmonicmean(vector(n, k, k*(5*k-3)/2)))); s
CROSSREFS
KEYWORD
nonn
AUTHOR
Colin Barker, Nov 19 2014
STATUS
approved