OFFSET
0,2
FORMULA
Conjectured linear recurrence: a(n) = 2*a(n-1) + a(n-2) - 4*a(n-3) + a(n-4) + 2*a(n-5) - a(n-6), with a(0) = 1, a(1) = 5, a(2) = 16, a(3) = 34, a(4) = 67, a(5) = 111, a(6) = 178.
Conjectured g.f.: (1 + 3*x + 5*x^2 + x^3 + 2*x^4)/((x - 1)^4*(x + 1)^2).
Conjecture: a(n) = (2*n^3+6*n^2+9*n+4+n*(-1)^n)/4. - Luce ETIENNE, Oct 16 2016
Conjectured e.g.f.: ((2 + 8*x + 6*x^2 + x^3)*cosh(x) + (2 + 9*x + 6*x^2 + x^3)*sinh(x))/2. - Stefano Spezia, May 10 2021
EXAMPLE
First 5 rows of A246694 preceded by sums
sum = 1: ...... 1;
sum = 5: ...... 2 ... 3;
sum = 16: ..... 5 ... 4 ... 7;
sum = 34: ..... 6 ... 9 ... 8 ... 11;
sum = 67: ..... 13 .. 10 .. 15 .. 12 .. 17.
MATHEMATICA
z = 25; t[0, 0] = 1; t[1, 0] = 2; t[1, 1] = 3; t[n_, 0] := t[n, 0] = If[OddQ[n], t[n - 1, n - 2] + 2, t[n - 1, n - 1] + 2]; t[n_, 1] := t[n, 1] = If[OddQ[n], t[n - 1, n - 1] + 2, t[n - 1, n - 2] + 2]
t[n_, k_] := t[n, k] = t[n, k - 2] + 2;
u = Flatten[Table[t[n, k], {n, 0, z}, {k, 0, n}]] (* A246696 *)
Table[Sum[t[n, k], {k, 0, n}], {n, 0, 2*z}] (* A246697 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Sep 02 2014
EXTENSIONS
Corrected and edited by M. F. Hasler, Nov 17 2014
STATUS
approved