OFFSET
0,2
LINKS
Colin Barker, Table of n, a(n) for n = 0..900
Index entries for linear recurrences with constant coefficients, signature (21,-120,100).
FORMULA
From Colin Barker, Oct 29 2017: (Start)
G.f.: (1 - 12*x + 10*x^2) / ((1 - x)*(1 - 10*x)^2).
a(n) = 21*a(n-1) - 120*a(n-2) + 100*a(n-3) for n>2.
(End)
EXAMPLE
Curious multiplications:
9 * 8 = 72;
79 * 8 = 632;
679 * 8 = 5432;
5679 * 8 = 45432;
45679 * 8 = 365432;
345679 * 8 = 2765432;
2345679 * 8 = 18765432.
9 * 9 = 81;
79 * 9 = 711;
679 * 9 = 6111;
5679 * 9 = 51111;
45679 * 9 = 411111;
345679 * 9 = 3111111;
2345679 * 9 = 21111111.
MATHEMATICA
LinearRecurrence[{21, -120, 100}, {1, 9, 79}, 30] (* Harvey P. Dale, Mar 12 2018 *)
PROG
(PARI) Vec((1 - 12*x + 10*x^2) / ((1 - x)*(1 - 10*x)^2) + O(x^30)) \\ Colin Barker, Oct 29 2017
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Seiichi Manyama, Oct 28 2017
STATUS
approved