OFFSET
0,1
COMMENTS
Numerator of (2*n+7)*(3*n^4 + 42*n^3 + 203*n^2 + 392*n + 252)/((n+1)*(n+2)*...*(n+6)).
(2*n+7)*(3*n^4 + 42*n^3 + 203*n^2 + 392*n + 252)/a(n) can be factored into 2^m(n)*3^p(n)*5^(q1(n) + q2(n)) where
m(n) is of period 4, repeating [2,2,3,3]
p(n) is of period 9, repeating [2,2,2,1,1,1,1,1,1]
q1(n) is of period 5, repeating [0,0,0,0,1]
q2(n) is of period 25, repeating [0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0].
LINKS
Robert Israel, Table of n, a(n) for n = 0..10000
FORMULA
a(n) = (2*n+7)*(3*n^4 + 42*n^3 + 203*n^2 + 392*n + 252)/(2^(P(0,4,2,n)+2) * 3^(P(6,9,6,n)+1)*5^(P(0,5,4,n)+P(15,25,24,n))), where P(x,y,z,n) = floor(((n+x)mod y)/z).
MAPLE
h:= n-> sum(1/k, k=1..n):seq(numer(h(n+6)-h(n)), n=0..33);
P:=(x, y, z, n)-> floor(((n+x)mod y)/z):
a:=n->(2*n+7)*(3*n^4+42*n^3+203*n^2+392*n+252)/(2^(P(0, 4, 2, n)+2)*3^(P(6, 9, 6, n)+1)*5^(P(0, 5, 4, n)+P(15, 25, 24, n))):
seq(a(n), n=0..25);
MATHEMATICA
Numerator[Table[HarmonicNumber[n+6]-HarmonicNumber[n], {n, 0, 40}]] (* Harvey P. Dale, Mar 27 2015 *)
PROG
(PARI) h(n) = sum(k=1, n, 1/k);
a(n) = numerator(h(n+6)-h(n)); \\ Michel Marcus, Apr 15 2017
(Magma) [49] cat [Numerator(HarmonicNumber(n+6) - HarmonicNumber(n)): n in [1..40]]; // G. C. Greubel, Oct 20 2018
(GAP) List(List([0..35], n->Sum([1..n+6], k->(1/k))-Sum([1..n], k->(1/k))), NumeratorRat); # Muniru A Asiru, Oct 21 2018
CROSSREFS
KEYWORD
AUTHOR
Gary Detlefs, Jun 28 2011
STATUS
approved