A281581 a(n) = (15*2^(2*n+2) + 15*2^(n+2) + 5*2^(n+3)*3^(n+1) - 24*5^(n+1))/120.

1, 4, 21, 127, 807, 5179, 33111, 210067, 1321887, 8255899, 51225351, 316067107, 1941032367, 11873549419, 72394874391, 440204293747, 2670669533247, 16172309991739, 97779619272231, 590423692897987, 3561340764760527, 21462312506478859

Offset: 0

Author

Seiichi Manyama, Mar 05 2017

Keywords

• nonn
• easy

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..1285
• Index entries for linear recurrences with constant coefficients, signature (17,-104,268,-240).

Crossrefs

Row n=5 of A283272.

Programs

Mathematica

Table[(15*2^(2*n+2) + 15*2^(n+2) + 5*2^(n+3)*3^(n+1) - 24*5^(n+1)) / 120, {n, 0, 21}] (* Indranil Ghosh, Mar 05 2017 *)

PARI

a(n) = (15*2^(2*n+2) + 15*2^(n+2) + 5*2^(n+3)*3^(n+1) - 24*5^(n+1)) / 120;
for (n=0, 21, print1(a(n),", ")); \\ Indranil Ghosh, Mar 05 2017

Python

def A281581(n): return (15*2**(2*n+2) + 15*2**(n+2) + 5*2**(n+3)*3**(n+1) - 24*5**(n+1)) / 120 # Indranil Ghosh, Mar 05 2017

Ruby

def A281581(n)
  (0..n).map{|i| (15 * 2 ** (2 * i + 2) + 15 * 2 ** (i + 2) + 5 * 2 ** (i + 3) * 3 ** (i + 1) - 24 * 5 ** (i + 1)) / 120}
end

Formula

G.f.: ( 1-13*x+57*x^2-82*x^3 ) / ( (6*x-1)*(4*x-1)*(2*x-1)*(5*x-1) ). - R. J. Mathar, Mar 19 2017

a(n) = 6^n +2^(n-1)-5^n+4^n/2. - R. J. Mathar, Mar 19 2017