|
Search: id:A108368
|
|
|
| A108368 |
|
Coefficients of x/(1-3*x-3*x^2-x^3). |
|
+0
2
|
|
| 0, 1, 3, 12, 46, 177, 681, 2620, 10080, 38781, 149203, 574032, 2208486, 8496757, 32689761, 125768040, 483870160, 1861604361, 7162191603, 27555258052, 106013953326, 407869825737, 1569206595241, 6037243216260, 23227219260240
(list; graph; listen)
|
|
|
OFFSET
|
0,3
|
|
|
REFERENCES
|
L. E. Dickson, History of the Theory of Numbers. Carnegie Institute Public. 256, Washington, DC, Vol. 1, 1919; Vol. 2, 1920; Vol. 3, 1923, see vol. 2, p. 562.
|
|
FORMULA
|
x=a(n), z=a(-n), y=a(n)+a(n-1), t=a(-n)+a(-n-1) is a solution to 2(x^3+z^3)=y^3+t^3.
G.f.: x/(1-3*x-3*x^2-x^3). a(n)=3a(n-1)+3a(n-2)+a(n-3). a(-1-n)=A108369(n).
|
|
PROGRAM
|
(PARI) {a(n)=if(n>=0, polcoeff(x/(1-3*x-3*x^2-x^3)+x*O(x^n), n), n=-1-n; polcoeff(x/(1+3*x+3*x^2-x^3)+x*O(x^n), n))}
|
|
CROSSREFS
|
Adjacent sequences: A108365 A108366 A108367 this_sequence A108369 A108370 A108371
Sequence in context: A026559 A008781 A047013 this_sequence A077829 A088132 A122450
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Michael Somos, Jun 01 2005
|
|
|
Search completed in 0.002 seconds
|
