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A175935
Number of lattice paths from (0,0) to (n,n) using steps S={(k,0),(0,k),(r,r)|0<k<=2,0<r<=2} which never go above the line y=x.
4
1, 2, 10, 55, 351, 2401, 17248, 128221, 978082, 7612155, 60204488, 482481220, 3909460725, 31974923487, 263623879118, 2188682538746, 18282238300443, 153537981720402, 1295640515428649, 10980400434511117, 93418283866708579
OFFSET
0,2
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric Werley, Dec 06 2010
STATUS
approved