



6, 21, 81, 321, 1281, 5121, 20481, 81921, 327681, 1310721, 5242881, 20971521, 83886081, 335544321, 1342177281, 5368709121, 21474836481, 85899345921, 343597383681, 1374389534721, 5497558138881, 21990232555521, 87960930222081
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OFFSET

0,1


COMMENTS

An Engel expansion of 4/5 to the base 4 as defined in A181565, with the associated series expansion 4/5 = 4/6 + 4^2/(6*21) + 4^3/(6*21*81) + 4^4/(6*21*81*321) + .... Cf. A136412 and A140660.  Peter Bala, Oct 29 2013


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (5,4).


FORMULA

a(n) = 3*A136412(n).
a(n) = 4*a(n1)3.
a(n) = 5*a(n1)4*a(n2).
G.f.: 3*(23*x)/((1x)*(14*x)).  Bruno Berselli, Nov 04 2011


PROG

(MAGMA) [5*4^n+1: n in [0..30]];


CROSSREFS

A136412, A140660, A199115.
Sequence in context: A255719 A134927 A108306 * A320649 A219596 A182251
Adjacent sequences: A199112 A199113 A199114 * A199116 A199117 A199118


KEYWORD

nonn,easy


AUTHOR

Vincenzo Librandi, Nov 04 2011


STATUS

approved



