login
A152418
A sevens sequence: a(n) = (7^n - 1)/(2^(4 - 3*(n mod 2))).
2
0, 3, 3, 171, 150, 8403, 7353, 411771, 360300, 20176803, 17654703, 988663371, 865080450, 48444505203, 42388942053, 2373780754971, 2077058160600, 116315256993603, 101775849869403, 5699447592686571, 4987016643600750
OFFSET
0,2
FORMULA
a(n) = (7^n - 1)/(2^(4 - 3*(n mod 2))).
a(n) = 50*a(n-2)-49*a(n-4). - Colin Barker, Nov 06 2014
G.f.: 3*x*(7*x^2+x+1) / ((x-1)*(x+1)*(7*x-1)*(7*x+1)). - Colin Barker, Nov 06 2014
MATHEMATICA
a[n_] := (7^n - 1)/(2^(4 - 3*Mod[n, 2]));
Table[a[n], {n, 0, 30}]
PROG
(PARI) concat(0, Vec(3*x*(7*x^2+x+1)/((x-1)*(x+1)*(7*x-1)*(7*x+1)) + O(x^100))) \\ Colin Barker, Nov 06 2014
CROSSREFS
Cf. A003462.
Sequence in context: A006845 A071536 A094755 * A273925 A113457 A113466
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Dec 03 2008
STATUS
approved