5,2

With a different offset, number of n-permutations of 6 objects:t,u,v,z,x, y with repetition allowed, containing exactly five (5) u's. Example: a(1)=30 because we have uuuuut, uuuutu, uuutuu, uutuuu, utuuuu, tuuuuu, uuuuuv, uuuuvu, uuuvuu, uuvuuu, uvuuuu, vuuuuu, uuuuuz, uuuuzu, uuuzuu, uuzuuu, uzuuuu, zuuuuu, uuuuux, uuuuxu, uuuxuu, uuxuuu, uxuuuu, xuuuuu, uuuuuy, uuuuyu, uuuyuu, uuyuuu, uyuuuu, yuuuuu. - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 16 2008

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 91, #43..

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

C(n, 5)*5^(n-5).

seq(binomial(n+5, 5)*5^n, n=0..17); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 16 2008

Cf. A000027, A001788, A036216, A040075, A050988, A050989.

Sequence in context: A118681 A020926 A022754 this_sequence A004327 A139626 A037961

Adjacent sequences: A050979 A050980 A050981 this_sequence A050983 A050984 A050985

nonn

Eric Weisstein (eric(AT)weisstein.com)