OFFSET
0,2
COMMENTS
Diagonal sums of Riordan array ((1-x)/(1+x),x/(1+x)^2), A110162.
The positive sequence with g.f. (1-x^2)/(1-2x) gives the row sums of the Riordan array (1+x,x/(1-x)). - Paul Barry, Jul 18 2005
The inverse g.f. is (1 + 2*x + x^2 + 2*x^3 + x^4 + 2*x^5 + x^6 + ...). - Gary W. Adamson, Jan 07 2011
LINKS
FORMULA
a(n) = 3*(-2)^(n-2) = 3*A122803(n-2) for n >= 2. a(n) = -2 a(n-1) for n >= 3. - M. F. Hasler, Apr 19 2015
E.g.f.: (1/4) - (x/2) + (3/4)*exp(-2*x). - Alejandro J. Becerra Jr., Jan 29 2021
MATHEMATICA
CoefficientList[Series[(1 - x^2)/(1 + 2x), {x, 0, 33}], x] (* Robert G. Wilson v, Jul 08 2006 *)
LinearRecurrence[{-2}, {1, -2, 3}, 40] (* Harvey P. Dale, May 10 2023 *)
PROG
(PARI) A110164(n)=if(n>1, 3*(-2)^(n-2), 1-3*n) \\ M. F. Hasler, Apr 19 2015
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Jul 14 2005
STATUS
approved