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COMMENTS
| 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.
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PROG
| (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]
(MAGMA) [6^n* Binomial(n+4, 4): n in [0..20]]; // Vincenzo Librandi, Oct 12 2011
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