OFFSET
1,2
COMMENTS
Sums are built along inclined lines through the triangle with (1,2)-steps in the (row,column) indices. - R. J. Mathar, Aug 19 2010
LINKS
Index entries for linear recurrences with constant coefficients, signature (11,-9,-10).
FORMULA
From R. J. Mathar, Aug 19 2010: (Start)
G.f.: ( 1-x ) / ( (10*x-1)*(x^2+x-1) ).
a(n) = +11*a(n-1) -9*a(n-2) -10*a(n-3).
a(n) = (90*10^n -A022100(n))/89. (End)
EXAMPLE
From R. J. Mathar, Aug 19 2010: (Start)
One example is a(5), the sum of numbers in parentheses:
1;
1, 10;
(1), 11, 100;
1, 12, (111) ; 1000;;
1, 13, 123 ; 1111, (10000); (End)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mark Dols, Aug 15 2010
EXTENSIONS
More terms from R. J. Mathar, Aug 19 2010
STATUS
approved