OFFSET
0,2
COMMENTS
Difference table:
0, 3, 13, 32, 59, 93, 136, 187, ...
3, 10, 19, 27, 34, 43, 51, ... = b(n)
7, 9, 8, 7, 9, 8, ... .
The sequence of last decimal digits of a(n) has period 15 and contain no 1's, 4's or 8's.
a(n) is e(n), hexasection, in A262397(n-1).
b(n) mod 9 is of period 9: 3, 1, 1, 0, 7, 7, 6, 4, 4.
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-2,1).
FORMULA
a(-n) = A262997(n).
a(n) = 2*a(n-1) - a(n-2) + a(n-3) - 2*a(n-4) + a(n-5).
Trisections: a(3n) = 4*n*(9*n-1), a(3n+1) = 3 + 20*n + 36*n^2, a(3n+2) = 13 + 44*n + 36*n^2.
a(n+15) = a(n) + 40*(22+3*n).
G.f.: x*(1 + x)*(3 + 4*x + 5*x^2) / ((1 - x)^3*(1 + x + x^2)). - Colin Barker, Jun 20 2018
MATHEMATICA
CoefficientList[ Series[ -x (5^3 +9x^2 +7x +3)/(x -1)^3 (x^2 +x +1), {x, 0, 40}], x] (* or *)LinearRecurrence[{2, -1, 1, -2, 1}, {0, 3, 13, 32, 59, 93}, 41] (* Robert G. Wilson v, Jun 20 2018 *)
PROG
(PARI) concat(0, Vec(x*(1 + x)*(3 + 4*x + 5*x^2) / ((1 - x)^3*(1 + x + x^2)) + O(x^40))) \\ Colin Barker, Jun 20 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Jun 20 2018
STATUS
approved