0,2

With a different offset, number of n-permutations (n=5) of 7 objects t, u, v, w, z, x, y with repetition allowed, containing exactly four (4)u's. Example: a(1)=30 because we have

uuuut, uuutu, uutuu, utuuu, tuuuu,

uuuuv, uuuvu, uuvuu, uvuuu, vuuuu,

uuuuw, uuuwu, uuwuu, uwuuu, wuuuu,

uuuuz, uuuzu, uuzuu, uzuuu, zuuuu,

uuuux, uuuxu, uuxuu, uxuuu, xuuuu,

uuuuy, uuuyu, uuyuu, uyuuu, yuuuu.

seq(binomial(n+4, 4)*6^n, n=0..22);

(Other) SAGE:[lucas_number2(n, 6, 0)*binomial(n, 4)/6^4for n in xrange(4, 22)] [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 13 2009]

Sequence in context: A022754 A050982 A004327 this_sequence A037961 A143399 A075510

Adjacent sequences: A139623 A139624 A139625 this_sequence A139627 A139628 A139629

nonn

Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 12 2008