A164872 The number of permutations of length n that can be sorted by 4 pop stacks in parallel.

1, 2, 6, 24, 120, 718, 4884, 35546, 264590, 1969912, 14560996, 106781758, 778073440, 5643649364, 40811356112, 294554236798, 2123419108962, 15296729408614, 110149122090326, 792974948890068, 5707931771206042

Offset

1,2

Links

Table of n, a(n) for n=1..21.

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

Formula

G.f.: (1584*x^11-14016*x^10+45432*x^9-79454*x^8+86562*x^7-62624*x^6 +30887*x^5-10411* x^4+2352*x^3-339*x^2+28*x-1) / (7920*x^11-40116*x^10 +96324*x^9-139728*x^8+133468 *x^7-87278*x^6+39670*x^5-12495*x^4 +2666*x^3-366*x^2+29*x-1).

Crossrefs

Sequence in context: A324132 A177524 A223905 * A226437 A224287 A248838

Adjacent sequences: A164869 A164870 A164871 * A164873 A164874 A164875

Keyword

nonn

Author

Vincent Vatter, Aug 29 2009

Status

approved