OFFSET
0,3
EXAMPLE
G.f.: A(x) = 1 + x + 3*x^2 + 12*x^3 + 56*x^4 + 284*x^5 + 1520*x^6 +...
where
A(x) = 1 + x*A(x) + x^2*A(x)^2 + x^3*A(x)^4 + x^4*A(x)^7 + x^5*A(x)^8 + x^6*A(x)^11 + x^7*A(x)^13 + x^8*A(x)^14 +...
and exponents A000069(n) begin:
[1,2,4,7,8,11,13,14,16,19,21,22,25,26,28,31,32,35,37,38,41,...].
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Sep 13 2011
STATUS
approved