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A164872 The number of permutations of length n that can be sorted by 4 pop stacks in parallel 0
1, 2, 6, 24, 120, 718, 4884, 35546, 264590, 1969912, 14560996, 106781758, 778073440, 5643649364, 40811356112, 294554236798, 2123419108962, 15296729408614, 110149122090326, 792974948890068, 5707931771206042 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 22 20:47 EDT 2019. Contains 326209 sequences. (Running on oeis4.)