OFFSET
0,2
LINKS
Jean-François Alcover, Table of n, a(n) for n = 0..1000
Wikipedia, Quasi-polynomial
FORMULA
G.f.: -(x^18 +3*x^17 +12*x^16 -6*x^15 +9*x^14 +91*x^12 -138*x^11 +183*x^10 -134*x^9 +183*x^8 -138*x^7 +91*x^6 +9*x^4 -6*x^3 +12*x^2 +3*x +1) / ((x -1)^3*(x^2 +1)^3*(x^4 +1)^3). - Colin Barker, Oct 09 2014 [Confirmed by Peter Bala, Feb 27 2019]
From Peter Bala, Feb 26 2019: (Start)
a(n) = 4*(n + 1)*(n + 2)/gcd(4*(n + 1)*(n + 2), n*(n + 3)).
a(n ) is quasi-polynomial in n; a(n) = (n + 1)*(n + 2)/2 when n = 0, 5 (mod 8); a(n) = (n + 1)*(n + 2) when n = 1, 4 (mod 8); a(n) = 2*(n + 1)*(n + 2) when n = 2, 3, 6, 7 (mod 8).
(End)
MAPLE
seq( 4*(n + 1)*(n + 2)/igcd(4*(n + 1)*(n + 2), n*(n + 3)), n = 0..100); - Peter Bala, Feb 26 2019
MATHEMATICA
Table[Denominator[n*(n+3)/(4*(n+1)*(n+2))], {n, 0, 100}]
PROG
(PARI) vector(100, n, denominator((n-1)*(n+2)/(4*n*(n+1)))) \\ Colin Barker, Oct 09 2014
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
Jean-François Alcover, Oct 16 2013
STATUS
approved