login
A165188
Interleaving of A014125 and zero followed by A014125.
4
1, 0, 3, 1, 6, 3, 11, 6, 18, 11, 27, 18, 39, 27, 54, 39, 72, 54, 94, 72, 120, 94, 150, 120, 185, 150, 225, 185, 270, 225, 321, 270, 378, 321, 441, 378, 511, 441, 588, 511, 672, 588, 764, 672, 864, 764, 972, 864, 1089, 972, 1215, 1089, 1350, 1215, 1495, 1350
OFFSET
1,3
COMMENTS
This sequence convolved with A000217 (without initial term 0) yields A164680.
See A164680 for similar convolutions.
A165188 convolved with A000217 yields sequence A164680. This is to be expected since A000217 can be associated with partition 1+1+1, A164680 with partition 1+1+1+2+2+2+3 and A165188 with partition 2+2+2+3 by observing their unreduced generating functions and verified by generating the sequences by converting the partitions into finite sequences and using Euler's Transform. Thus partition 1+1+1 yields the finite sequence (3); partition 2+2+2+3 yields the finite sequence (0,3,1); and, when combined, partition 1+1+1+2+2+2+3 yields (3,3,1). - Alford Arnold, Sep 24 2009
FORMULA
a(n) = -a(n-1)+2*a(n-2)+3*a(n-3)-3*a(n-5)-2*a(n-6)+a(n-7)+a(n-8)+1 for n > 8; a(1)=1, a(2)=0, a(3)=3, a(4)=1, a(5)=6, a(6)=3, a(7)=11, a(8)=6. - Klaus Brockhaus, Sep 15 2009
G.f.: x/((1-x)^4*(1+x)^3*(1+x+x^2)). - Klaus Brockhaus, Sep 15 2009
a(n) = (2*n^3+21*n^2+63*n+49)/288-(-1)^n*(9+7*n+n^2)/32+A057078(n)/9. - R. J. Mathar, Sep 17 2009
Euler transform of length 3 sequence [ 0, 3, 1]. - Michael Somos, Feb 01 2015
G.f.: x / ((1 - x^2)^3 * (1 - x^3)). - Michael Somos, Feb 01 2015
a(n) = -a(-7 - n) for all n in Z.
a(n+3) - a(n) = 0 if n odd else (n+6) * (n+4) / 8. - Michael Somos, Feb 01 2015
a(2*n + 1) = a(2*n + 4) = A014125(n) for all n in Z. - Michael Somos, Feb 01 2015
EXAMPLE
A014125 begins 1,3,6,11,18,27,..., thus this sequence begins 1,0,3,1,6,3,11,6,18,11,27,18,... .
G.f. = x + 3*x^3 + x^4 + 6*x^5 + 3*x^6 + 11*x^7 + 6*x^8 + 18*x^9 + 11*x^10 + ...
MATHEMATICA
a[ n_] := Module[{s = 1, m = n}, If[ n < 0, s = -1; m = -7 - n]; s SeriesCoefficient[ x / ((1 - x^2)^3 (1 - x^3)), {x, 0, m}]]; (* Michael Somos, Feb 01 2015 *)
LinearRecurrence[{0, 3, 1, -3, -3, 1, 3, 0, -1}, {1, 0, 3, 1, 6, 3, 11, 6, 18}, 60] (* Harvey P. Dale, Apr 14 2018 *)
PROG
(PARI) /* first computes u = A014125 as second bisection of A001400, then interleaves */ {m=28; u=vector(m, n, polcoeff(1/((1-x)*(1-x^2)*(1-x^3)*(1-x^4))+O(x^(2*n)), 2*n-1)); vector(2*m, k, if(k%2==1, u[(k+1)/2], if(k==2, 0, u[k/2-1])))} /* Klaus Brockhaus, Sep 15 2009 */
(PARI) {a(n) = my(s=1); if( n<0, s=-1; n=-7-n); s * polcoeff( x / ((1 - x^2)^3 * (1 - x^3)) + x * O(x^n), n)}; /* Michael Somos, Feb 01 2015 */
(Magma) I:=[1, 0, 3, 1, 6, 3, 11, 6]; [n le 8 select I[n] else -Self(n-1)+2*Self(n-2)+3*Self(n-3)-3*Self(n-5)-2*Self(n-6)+Self(n-7)+Self(n-8)+1: n in [1..60]]; // Vincenzo Librandi, Jun 24 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Alford Arnold, Sep 13 2009
EXTENSIONS
Edited and extended by Klaus Brockhaus, Sep 15 2009
Linear recurrence link and signature correct by Michel Marcus, Jun 25 2015
STATUS
approved