A263044 a(1) = a(2) = a(3) = 1; for n>3, a(n) = (a(n-3) + a(n-1))*(a(n-2) + a(n-3)).

1, 1, 1, 4, 10, 55, 826, 54340, 47921995, 2643710343286, 126835535679488180710, 335322495784116748418182251685105, 42530809264656915340847577048392358554130713446770436

Offset: 1

Author

Gianmarco Giordano, Oct 08 2015

Keywords

• nonn

Programs

Magma

[n le 3 select 1  else (Self(n-3)+ Self(n-1))*(Self(n-2)+Self(n-3)): n in [1..15]]; // Vincenzo Librandi, Oct 09 2015

Mathematica

RecurrenceTable[{a[1] == a[2] == a[3] == 1, a[n] == (a[n - 3] + a[n - 1]) (a[n - 2] + a[n - 3])}, a, {n, 15}] (* Bruno Berselli, Oct 09 2015 *)

PARI

a(n) = if(n<4, 1, (a(n-3)+a(n-1))*(a(n-2)+a(n-3)));
vector(15, n, a(n)) \\ Altug Alkan, Oct 08 2015

Formula

a(n) = (a(n-3) + a(n-1))*(a(n-2) + a(n-3)) for n>=4; a(1)=a(2)=a(3)=1.

Extensions

More terms from Altug Alkan, Oct 08 2015