A122591 a(n) = 2*a(n-1) - a(n-2) + (a(n-1)^2 + a(n-2)^2).

1, 1, 3, 15, 261, 68853, 4740941175, 22476523239032929731, 505194096914787342916581691483319031273, 255221075557547546310804864838512137564534415781651685947633570258183940865705

Offset

1,3

Links

G. C. Greubel, Table of n, a(n) for n = 1..13

Formula

a(n) = 2*a(n-1) - a(n-2) + (a(n-1)^2 + a(n-2)^2), with a(1) = a(2) = 1.

Mathematica

a[n_]:= a[n]= If[n<3, 1, 2*a[n-1] -a[n-2] +(a[n-1]^2 + a[n-2]^2)];
Table[a[n], {n, 0, 10}]

Prog

(Magma)
function a(n) // a = A122591
  if n lt 3 then return 1;
  else return 2*a(n-1) -a(n-2) +(a(n-1)^2 +a(n-2)^2);
  end if; return a; end function;
[a(n): n in [1..12]]; // G. C. Greubel, Nov 29 2021
(Sage)
#a = A122591
def a(n): return 1 if (n<3) else 2*a(n-1) -a(n-2) +(a(n-1)^2 +a(n-2)^2)
[a(n) for n in (1..12)] # G. C. Greubel, Nov 29 2021

Crossrefs

Cf. A122590, A122592, A122593.

Sequence in context: A051179 A374341 A374342 * A326263 A120607 A013352

Adjacent sequences: A122588 A122589 A122590 * A122592 A122593 A122594

Keyword

nonn

Author

Roger L. Bagula, Sep 19 2006

Extensions

Edited by N. J. A. Sloane, Sep 21 2006

Status

approved