0,2

Also minimal 3-covers of a labeled n-set that cover 3 points of that set uniquely (if offset is 3). Cf. A057524 for unlabeled case - Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 02 2000

Also convolution of A020918 with A000984 (central binomial coefficients)

Let M=[1,0,0,i;0,1,i,0;0,i,1,0;i,0,0,1], i=sqrt(-1). Then 1/det(I-xM)=1/(1-4x)^4. - Paul Barry (pbarry(AT)wit.ie), Apr 27 2005

With a different offset, number of n-permutations (n=4)of 5 objects u, v, w, z, x with repetition allowed, containing exactly three u's. Example: a(1)=16 because we have uuuv, uuvu, uvuu, vuuu, uuuw, uuwu, uwuu, wuuu, uuuz, uuzu, uzuu, zuuu, uuux, uuxu, uxuu and xuuu - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 19 2008

From A152818. a(n)=A006044/6. [From Paul Curtz (bpcrtz(AT)free.fr), Jan 07 2009]

a(n)=binomial(n+3, 3)*4^n; G.f. 1/(1-4*x)^4.

a(n) = sum( a+b+c+d+e+f+g+h=n, f(a)*f(b)*f(c)*f(d)*f(e)*f(f)*f(g)*f(h)) with f(n)=A000984(n) . - DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Jan 22 2004

seq(seq(binomial(i, j)*4^(i-3), j =i-3), i=3..22); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 03 2007

seq(binomial(n+3, 3)*4^n, n=0..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 19 2008

(Other) SAGE: [lucas_number2(n, 4, 0)*binomial(n, 3)/2^6 for n in xrange(3, 26)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 11 2009]

Cf. A000302, A020918, A000984.

Cf. A038231.

Sequence in context: A144453 A121036 A073394 this_sequence A079767 A079768 A053410

Adjacent sequences: A038843 A038844 A038845 this_sequence A038847 A038848 A038849

easy,nonn

Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de)