OFFSET
1,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..50
Eric Weisstein's World of Mathematics, Dominating Set
PROG
(PARI)
Collect(sig, v, r, x)={forstep(r=r, 1, -1, my(w=sig[r]+1); v=vector(#v, k, sum(j=1, k, binomial(#v-j, k-j)*v[j]*x^(k-j)*(1+x)^(w-#v+j-1))-v[k])); v[#v]}
DomSetCount(sig, x)={my(v=[1]); my(total=Collect(sig, v, #sig, x)); forstep(r=#sig, 1, -1, my(w=sig[r]+1); total+=Collect(sig, vector(w, k, if(k<=#v, v[k])), r-1, x); v=vector(w, k, sum(j=1, min(k, #v), binomial(w-j, k-j)*v[j]*x^(k-j)*(1+x)^(j-1)))); total}
a(n)=DomSetCount(Vecrev([1..n]), 1); \\ Andrew Howroyd, Nov 05 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Aug 14 2017
EXTENSIONS
Terms a(8) and beyond from Andrew Howroyd, Nov 05 2017
STATUS
approved