0,2

With a different offset, number of n-permutations (n>=7) of 6 objects: t, u, v, z, x, y with repetition allowed, containing exactly seven (7) u's.

If n=7 then a(0)= 1

Example: a(1)=40 because we have

uuuuuuut, uuuuuuuv, uuuuuuuz, uuuuuuux, uuuuuuuy,

uuuuuutu, uuuuuuvu, uuuuuuzu, uuuuuuxu, uuuuuuyu,

uuuuutuu, uuuuuvuu, uuuuuzuu, uuuuuxuu, uuuuuyuu,

uuuutuuu, uuuuvuuu, uuuuzuuu, uuuuxuuu, uuuuyuuu,

uuutuuuu, uuuvuuuu, uuuzuuuu, uuuxuuuu, uuuyuuuu,

uutuuuuu, uuvuuuuu, uuzuuuuu, uuxuuuuu, uuyuuuuu,

utuuuuuu, uvuuuuuu, uzuuuuuu, uxuuuuuu, uyuuuuuu,

tuuuuuuu, vuuuuuuu, zuuuuuuu, xuuuuuuu, yuuuuuuu.

seq(binomial(n+7, 7)*5^n, n=0..18);

(Other) SAGE: [lucas_number2(n, 5, 0)*binomial(n, 7)/5^7 for n in xrange(7, 25)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 12 2009]

Sequence in context: A013346 A013348 A013349 this_sequence A130610 A004339 A004349

Adjacent sequences: A140217 A140218 A140219 this_sequence A140221 A140222 A140223

nonn

Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 23 2008