1,2

R. Smith and V. Vatter, The enumeration of permutations sortable by pop stacks in parallel

G.f.: (2*x^3-6*x^2+5*x-1)/(-1+6*x-10*x^2+6*x^3)

Sequence in context: A150241 A150242 A150243 this_sequence A121686 A128723 A150244

Adjacent sequences: A164867 A164868 A164869 this_sequence A164871 A164872 A164873

nonn

Vince Vatter (vatter(AT)gmail.com), Aug 29 2009