

A166481


a(n) = 3*a(n2) for n > 2; a(1) = 1; a(2) = 7.


1



1, 7, 3, 21, 9, 63, 27, 189, 81, 567, 243, 1701, 729, 5103, 2187, 15309, 6561, 45927, 19683, 137781, 59049, 413343, 177147, 1240029, 531441, 3720087, 1594323, 11160261, 4782969, 33480783, 14348907, 100442349, 43046721, 301327047
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Interleaving of A000244 and A005032.
Seventh binomial transform is A153598.


LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200
Index entries for linear recurrences with constant coefficients, signature (0,3).


FORMULA

a(n) = (5+2*(1)^n)*3^(1/4*(2*n5+(1)^n)).
G.f.: x*(1+7*x)/(13*x^2).


MATHEMATICA

LinearRecurrence[{0, 3}, {1, 7}, 50] (* or *) Flatten[NestList[3#&, {1, 7}, 20]] (* Harvey P. Dale, Sep 24 2015 *)


PROG

(MAGMA) [ n le 2 select 6*n5 else 3*Self(n2): n in [1..34] ];


CROSSREFS

Cf. A000244 (powers of 3), A005032 (7*3^n), A153598.
Sequence in context: A050013 A161417 A070409 * A050012 A271573 A098231
Adjacent sequences: A166478 A166479 A166480 * A166482 A166483 A166484


KEYWORD

nonn


AUTHOR

Klaus Brockhaus, Oct 14 2009


STATUS

approved



