0,2

If X_1, X_2, ..., X_n is a partition of the set {1,2,...,2*n} into blocks of size 2 then, for n>=1, a(n) is equal to the number of functions f : {1,2,..., 2*n}->{1,2,3,4,5} such that for fixed y_1,y_2,...,y_n in {1,2,3,4,5} we have f(X_i)<>{y_i}, (i=1,2,...,n). - Milan R. Janjic (agnus(AT)blic.net), May 24 2007

Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets

Tanya Khovanova, Recursive Sequences

Adjacent sequences: A009965 A009966 A009967 this_sequence A009969 A009970 A009971

Sequence in context: A007109 A077423 A059061 this_sequence A041265 A042106 A055359

nonn

njas