OFFSET
0,2
COMMENTS
With a different offset, number of n-permutations (n>=7) of 5 objects: u, v, z, x, y with repetition allowed, containing exactly seven (7) u's. - Zerinvary Lajos, Jun 23 2008
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..400
Index entries for linear recurrences with constant coefficients, signature (32,-448,3584,-17920,57344,-114688,131072,-65536).
FORMULA
a(n) = binomial(n+7, 7)*4^n.
G.f.: 1/(1-4*x)^8.
a(n) = A054335(n+15, 15).
E.g.f.: (315 + 8820*x + 52920*x^2 + 117600*x^3 + 117600*x^4 + 56448*x^5 + 12544*x^6 + 1024*x^7)*exp(4*x)/315. - G. C. Greubel, Jul 21 2019
From Amiram Eldar, Mar 27 2022: (Start)
Sum_{n>=0} 1/a(n) = 20412*log(4/3) - 88067/15.
Sum_{n>=0} (-1)^n/a(n) = 437500*log(5/4) - 292873/3. (End)
MAPLE
seq(binomial(n+7, 7)*4^n, n=0..20); # Zerinvary Lajos, Jun 23 2008
MATHEMATICA
Table[4^n*Binomial[n+7, 7], {n, 0, 20}] (* G. C. Greubel, Jul 21 2019 *)
PROG
(Magma) [4^n*Binomial(n+7, 7): n in [0..20]]; // Vincenzo Librandi, Oct 15 2011
(PARI) vector(20, n, n--; 4^n*binomial(n+7, 7)) \\ G. C. Greubel, Jul 21 2019
(GAP) List([0..20], n-> 4^n*Binomial(n+7, 7) ); # G. C. Greubel, Jul 21 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Wolfdieter Lang, Mar 13 2000
STATUS
approved