

A254660


Numbers of words on alphabet {0,1,...,6} with no subwords ii, where i is from {0,1,...,4}.


5



1, 7, 44, 278, 1756, 11092, 70064, 442568, 2795536, 17658352, 111541184, 704563808, 4450465216, 28111918912, 177572443904, 1121658501248, 7085095895296, 44753892374272, 282693546036224, 1785669060965888, 11279401457867776, 71247746869138432
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OFFSET

0,2


LINKS

Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (6,2).


FORMULA

G.f.: (1 + x)/(1  6*x 2*x^2).
a(n) = 6*a(n1) + 2*a(n2) with n>1, a(0) = 1, a(1) = 7.
a(n) = ((3sqrt(11))^n*(4+sqrt(11)) + (3+sqrt(11))^n*(4+sqrt(11))) / (2*sqrt(11)).  Colin Barker, Jan 21 2017


MATHEMATICA

RecurrenceTable[{a[0] == 1, a[1] == 7, a[n] == 6 a[n  1] + 2 a[n  2]}, a[n], {n, 0, 20}]


PROG

(PARI) Vec((1 + x) / (1  6*x 2*x^2) + O(x^30)) \\ Colin Barker, Jan 21 2017


CROSSREFS

Cf. A135030, A126473, A126501, A126528, A254598, A254602.
Sequence in context: A190974 A027279 A099464 * A093738 A091127 A166775
Adjacent sequences: A254657 A254658 A254659 * A254661 A254662 A254663


KEYWORD

nonn,easy


AUTHOR

Milan Janjic, Feb 04 2015


STATUS

approved



