login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A214068
a(n) = floor((3/2)*floor((3/2)*n)).
4
0, 1, 4, 6, 9, 10, 13, 15, 18, 19, 22, 24, 27, 28, 31, 33, 36, 37, 40, 42, 45, 46, 49, 51, 54, 55, 58, 60, 63, 64, 67, 69, 72, 73, 76, 78, 81, 82, 85, 87, 90, 91, 94, 96, 99, 100, 103, 105, 108, 109, 112, 114, 117, 118, 121, 123, 126
OFFSET
0,3
COMMENTS
Also, numbers congruent to {0,1,4,6} mod 9.
FORMULA
a(n) = (18*n - 5 + 3*(-1)^n + (1 - i)*(-i)^n + (1 + i)*i^n)/8, where i = sqrt(-1).
a(n) = a(n-1) + a(n-4) - a(n-5).
G.f.: (x*(1 + 3*x + 2*x^2 + 3*x^3))/(1 - x - x^4 + x^5).
MATHEMATICA
f[n_]:=Floor[(3/2)Floor[3n/2]];
t=Table[f[n], {n, 0, 70}]
LinearRecurrence[{1, 0, 0, 1, -1}, {0, 1, 4, 6, 9}, 60] (* Harvey P. Dale, Jun 21 2021 *)
CROSSREFS
Sequence in context: A189167 A283794 A287003 * A330182 A330186 A284654
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Jul 20 2012
STATUS
approved