OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).
FORMULA
a(n) = n*(n+1)*(n+2)*Stirling2(4 + n, 3 + n).
-a(-n-4) = a(n) for n >= 0.
a(n) = 60*A000389(n+4). - G. C. Greubel, Nov 20 2017
From Colin Barker, Nov 21 2017: (Start)
G.f.: 60*x / (1 - x)^6.
a(n) = (1/2)*(n*(1 + n)*(2 + n)*(3 + n)*(4 + n)).
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>5.
(End)
MATHEMATICA
LinearRecurrence[{6, -15, 20, -15, 6, -1}, {0, 60, 360, 1260, 3360, 7560}, 32]
Table[Pochhammer[n, 5]/2, {n, 0, 50}] (* G. C. Greubel, Nov 20 2017 *)
PROG
(PARI) for(n=0, 30, print1(n*(n+1)*(n+2)*stirling(4 + n, 3 + n, 2), ", ")) \\ G. C. Greubel, Nov 20 2017
(Magma) [0] cat [Factorial(n+4)/(2*Factorial(n-1)): n in [1..30]]; // G. C. Greubel, Nov 20 2017
(PARI) concat(0, Vec(60*x / (1 - x)^6 + O(x^40))) \\ Colin Barker, Nov 21 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Peter Luschny, Oct 20 2017
STATUS
approved