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 A266734 Number of words on {1,1,2,2,3,3,...,n,n} avoiding the pattern 1234. 10
 1, 1, 6, 90, 1879, 47024, 1331664, 41250519, 1367533365, 47808569835, 1744233181074, 65905305836049, 2564220925607625, 102277575120518170, 4167486279986250932, 172988069360147449566, 7298137818882637998561, 312349784398279829229533, 13539988681466075755541070 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..580 Ferenc Balogh, A generalization of Gessel's generating function to enumerate words with double or triple occurrences in each letter and without increasing subsequences of a given length, preprint arXiv:1505.01389, 2015. Shalosh B. Ekhad and Doron Zeilberger, The Generating Functions Enumerating 12..d-Avoiding Words with r occurrences of each of 1,2, ..., n are D-finite for all d and all r, 2014 FORMULA Conjecture: +3*n*(620202643096396011773 -608794959941727250938*n +146949290712243118000*n^2) *(n+1)^2 *(2*n+1)^2 *a(n) -n*(94389117512395618060544*n^6 -419724075420172456531120*n^5 +442263508538458916585360*n^4 +229131363207555256548194*n^3 -477880029525553894746823*n^2 +160086316440678171209939*n -11163647575735128211914) *a(n-1) -3*(n-1) *(23820522077322908587584*n^6 -1446304460086201780480376*n^5 +11080409117453774846145540*n^4 -35494287160655892321199502*n^3 +57163416479212379649118767*n^2 -45988763994280198223305139*n +14778623468656583258390502) *a(n-2) +36*(n-2) *(41902292735037258217056*n^6 -783254865433733876219472*n^5 +5235970136340811777332552*n^4 -17094365117036393449118734*n^3 +29518557363755878023892305*n^2 -25895204716899392803468055*n +9075752633781608162944050) *a(n-3) -8748*(n-2) *(125877543736438014048*n^2 -450267700517870762570*n +370949541619209268475) *(n-3)^2 *(2*n-7)^2 *a(n-4)=0. - R. J. Mathar, Apr 15 2016 CROSSREFS Cf. A220097, A266735. Column k=3 of A267479. Sequence in context: A006480 A138462 A002896 * A004996 A001499 A147630 Adjacent sequences:  A266731 A266732 A266733 * A266735 A266736 A266737 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 06 2016 EXTENSIONS More terms from Alois P. Heinz, Jan 14 2016 STATUS approved

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Last modified January 16 23:44 EST 2019. Contains 319206 sequences. (Running on oeis4.)