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A139641 a(n) = binomial(n+4, 4)*7^n. 5
1, 35, 735, 12005, 168070, 2117682, 24706290, 271769190, 2853576495, 28852829005, 282757724249, 2699051004195, 25191142705820, 230595844768660, 2075362602917940, 18401548412539068, 161013548609716845 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

With a different offset, number of n-permutations (n=5) of 8 objects s, t, u, v, w, z, x, y with repetition allowed, containing exactly four (4)u's. Example: a(1)=35 because we have

uuuus, uuusu, uusuu, usuuu, suuuu,

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.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..400

MAPLE

seq(binomial(n+4, 4)*7^n, n=0..20);

PROG

(Sage)[lucas_number2(n, 7, 0)*binomial(n, 4)/7^4for n in xrange(4, 21)] # Zerinvary Lajos, Mar 13 2009

(MAGMA) [7^n* Binomial(n+4, 4): n in [0..20]]; // Vincenzo Librandi, Oct 12 2011

CROSSREFS

Sequence in context: A140405 A278361 A145603 * A240928 A028220 A028213

Adjacent sequences:  A139638 A139639 A139640 * A139642 A139643 A139644

KEYWORD

nonn,easy

AUTHOR

Zerinvary Lajos, Jun 12 2008

STATUS

approved

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Last modified July 15 20:24 EDT 2019. Contains 325056 sequences. (Running on oeis4.)