OFFSET
0,2
COMMENTS
Exponential self-convolution of companion Pell numbers (A002203), divided by 4. - Vladimir Reshetnikov, Oct 07 2016
LINKS
Michael De Vlieger, Table of n, a(n) for n = 0..1463
Sergio Falcon, Half self-convolution of the k-Fibonacci sequence, Notes on Number Theory and Discrete Mathematics (2020) Vol. 26, No. 3, 96-106.
Index entries for linear recurrences with constant coefficients, signature (6,-4,-8).
FORMULA
G.f.: (1-4*x)/((1-2*x)*(1-4*x-4*x^2)).
E.g.f.: exp(2*x)*cosh(sqrt(2)*x)^2 = (exp(x)*cosh(sqrt(2)*x))^2.
a(n) = ((2+sqrt(8))^n + (2-sqrt(8))^n + 2^(n+1))/4.
a(n) = (A084128(n) + 2^n)/2.
a(n) = 2^(n-2)*(2 + A002203(n)). - Vladimir Reshetnikov, Oct 07 2016
a(n) = 6*a(n-1) - 4*a(n-2) - 8*a(n-3). - G. C. Greubel, Oct 13 2022
MATHEMATICA
Table[2^(n-2)*(2+LucasL[n, 2]), {n, 0, 20}] (* Vladimir Reshetnikov, Oct 07 2016 *)
PROG
(PARI) a(n)=if(n<0, 0, polsym(4+4*x-x^2, n)[n+1]/4+2^(n-1))
(Magma)
A002203:= func< n | Round((1+Sqrt(2))^n + (1-Sqrt(2))^n) >;
[2^(n-2)*(2+A002203(n)): n in [0..40]]; // G. C. Greubel, Oct 13 2022
(SageMath) [2^(n-2)*(2+lucas_number2(n, 2, -1)) for n in range(41)] # G. C. Greubel, Oct 13 2022
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, May 16 2003
STATUS
approved