A250345 - OEIS

%I #5 Nov 19 2014 10:42:59

%S 1,7,378,4284,294525,3180870,59376240,2510766720,2824612560,

%T 147507544800,2109357890640,43721236278720,1468304851693680,

%U 105943842376051680,113511259688626800,121078677001201920,5274489866864858640,161957865323732718240,3931977063692844326160

%N Numerator of the harmonic mean of the first n heptagonal numbers.

%H Colin Barker, <a href="/A250345/b250345.txt">Table of n, a(n) for n = 1..850</a>

%e a(3) = 378 because the first 3 heptagonal numbers are [1,7,18], and 3/(1/1+1/7+1/18) = 378/151.

%o (PARI)

%o harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])

%o s=vector(30); for(n=1, #s, s[n]=numerator(harmonicmean(vector(n, k, k*(5*k-3)/2)))); s

%Y Cf. A000566 (heptagonal numbers), A247115 (denominators).

%K nonn

%O 1,2

%A _Colin Barker_, Nov 19 2014