The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A183954 Number of strings of numbers x(i=1..3) in 0..n with sum i^2*x(i) equal to n*9. 2
1, 2, 2, 3, 4, 6, 7, 9, 12, 14, 17, 19, 22, 25, 29, 32, 36, 41, 45, 50, 54, 59, 64, 70, 75, 81, 88, 94, 101, 107, 114, 121, 129, 136, 144, 153, 161, 170, 178, 187, 196, 206, 215, 225, 236, 246, 257, 267, 278, 289, 301, 312, 324, 337, 349, 362, 374, 387, 400, 414, 427, 441 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Row 3 of A183953.
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-2) + a(n-9) - 2*a(n-10) + a(n-11).
Empirical g.f.: x*(1 + x)*(1 - x + x^3 - x^4 + 2*x^5 - 3*x^6 + 4*x^7 - 3*x^8 + x^9) / ((1 - x)^3*(1 + x + x^2)*(1 + x^3 + x^6)). - Colin Barker, Apr 07 2018
EXAMPLE
All solutions for n=3:
..0....1
..0....2
..3....2
MATHEMATICA
r[n_, k_, s_] := r[n, k, s] = Which[s < 0, 0, n == 0, If[s == 0, 1, 0], True, Sum[r[n - 1, k, s - c*n^2], {c, 0, k}]];
T[n_, k_] := r[n, k, k*n^2];
a[n_] := T[3, n];
Table[a[n], {n, 1, 62}] (* Jean-François Alcover, Jul 22 2022, after R. J. Mathar in A183953 *)
CROSSREFS
Cf. A183953.
Sequence in context: A119604 A036806 A039908 * A266747 A246762 A093950
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 08 2011
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 14 15:00 EDT 2024. Contains 373400 sequences. (Running on oeis4.)