OFFSET
1,2
FORMULA
Conjectures from Colin Barker, Feb 10 2020: (Start)
G.f.: x*(1 + x + 2*x^2 + 4*x^3 + x^4) / ((1 - x)^2*(1 + x)*(1 + x^2)).
a(n) = a(n-1) + a(n-4) - a(n-5) for n>5.
(End)
This g.f. follows from the observation that a(n+4) = a(n)+9 and this holds since the iterated sum of digits of N equals the iterated sum of digits of N+9. - Peter Bala, Feb 10 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
EXTENSIONS
More terms from Scott Lindhurst (ScottL(AT)alumni.princeton.edu)
Checked by Neven Juric (neven.juric(AT)apis-it.hr), Feb 04 2008
STATUS
approved