OFFSET
0,5
LINKS
Clark Kimberling, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,3,3,1).
FORMULA
a(n) = a(n-1) + 3*a(n-2) + 3*a(n-3) + a(n-4), where a(0) = a(1) = a(2) = a(3) = 1.
G.f.: (-1 + 3 x^2 + 6 x^3)/(-1 + x + 3 x^2 + 3 x^3 + x^4).
MATHEMATICA
LinearRecurrence[{1, 3, 3, 1}, {1, 1, 1, 1}, 50]
RecurrenceTable[{a[0]==a[1]==a[2]==a[3]==1, a[n]==a[n-1]+3a[n-2]+ 3a[n-3]+ a[n-4]}, a, {n, 30}] (* Harvey P. Dale, Apr 09 2022 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Aug 11 2016
STATUS
approved