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A152417 a(n) = (5^n - 1)/(2^(3 - (n mod 2))). 1
0, 1, 3, 31, 78, 781, 1953, 19531, 48828, 488281, 1220703, 12207031, 30517578, 305175781, 762939453, 7629394531, 19073486328, 190734863281, 476837158203, 4768371582031, 11920928955078, 119209289550781, 298023223876953, 2980232238769531, 7450580596923828 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0,26,0,-25).

FORMULA

a(n) = (5^n - 1)/(2^(3 - (n mod 2))).

From Colin Barker, Nov 16 2015: (Start)

a(n) = (5^n-1)/8 for n even.

a(n) = (5^n-1)/4 for n odd.

a(n) = 26*a(n-2)-25*a(n-4) for n>3.

G.f.: x*(5*x^2+3*x+1) / ((x-1)*(x+1)*(5*x-1)*(5*x+1)).

(End)

MATHEMATICA

a[n_] := (5^n - 1)/(2^(3 - Mod[n, 2]));

Table[a[n], {n, 0, 30}]

LinearRecurrence[{0, 26, 0, -25}, {0, 1, 3, 31}, 30] (* Harvey P. Dale, Aug 05 2018 *)

PROG

(PARI) concat(0, Vec(x*(5*x^2+3*x+1) / ((x-1)*(x+1)*(5*x-1)*(5*x+1)) + O(x^30))) \\ Colin Barker, Nov 16 2015

CROSSREFS

Cf. A003462.

Sequence in context: A031916 A137185 A243471 * A182232 A294973 A307711

Adjacent sequences:  A152414 A152415 A152416 * A152418 A152419 A152420

KEYWORD

nonn,easy

AUTHOR

Roger L. Bagula, Dec 03 2008

STATUS

approved

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Last modified August 24 16:15 EDT 2019. Contains 326295 sequences. (Running on oeis4.)