

A103376


a(1) = a(2) = a(3) = a(4) = a(5) = a(6) = a(7) = a(8) = a(9) = 1 and for n>9: a(n) = a(n8) + a(n9).


12



1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 4, 4, 4, 4, 4, 4, 4, 5, 7, 8, 8, 8, 8, 8, 8, 9, 12, 15, 16, 16, 16, 16, 16, 17, 21, 27, 31, 32, 32, 32, 32, 33, 38, 48, 58, 63, 64, 64, 64, 65, 71, 86, 106, 121, 127, 128, 128, 129, 136, 157, 192, 227, 248, 255, 256, 257, 265, 293
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OFFSET

1,10


COMMENTS

k=8 case of the family of sequences whose k=1 case is the Fibonacci sequence A000045, k=2 case is the Padovan sequence A000931 (offset so as to begin 1,1,1), k=3 case is A079398 (offset so as to begin 1,1,1,1), k=4 case is A103372, k=5 case is A103373, k=6 case is A103374 and k=7 case is A103375.
The general case for integer k>1 is defined: a(1) = a(2) = ... = a(k+1) and for n>(k+1) a(n) = a(nk) + a(n[k+1]).
For this k=8 case, the ratio of successive terms a(n)/a(n1) approaches the unique positive root of the characteristic polynomial: x^9  x  1 = 0. This is the real constant (to 50 digits accuracy): 1.0850702454914508283368958640973142340506536310308. Note that x = (1 + (1 + (1 + (1 + (1 + ...)^(1/9))^(1/9)))^(1/9))))^(1/9)))))^(1/9))))).
The sequence of prime values in this k=8 case is A103386; The sequence of semiprime values in this k=8 case is A103396.


REFERENCES

Zanten, A. J. van, "The golden ratio in the arts of painting, building and mathematics", Nieuw Archief voor Wiskunde, 4 (17) (1999) 229245.


LINKS

Table of n, a(n) for n=1..76.
J.P. Allouche and T. Johnson, Narayana's Cows and Delayed Morphisms
Richard Padovan, Dom Hans van der Laan and the Plastic Number.
E. S. Selmer, On the irreducibility of certain trinomials, Math. Scand., 4 (1956) 287302.
J. Shallit, A generalization of automatic sequences, Theoretical Computer Science, 61 (1988), 116.
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,1,1).


FORMULA

G.f.: x*(1+x)*(1+x^2)*(1+x^4)/(1x^8x^9).  R. J. Mathar, Dec 14 2009
a(1)=1, a(2)=1, a(3)=1, a(4)=1, a(5)=1, a(6)=1, a(7)=1, a(8)=1, a(9)=1, a(n)=a(n8)+a(n9).  Harvey P. Dale, May 07 2015


EXAMPLE

a(93) = 1200 because a(93) = a(938) + a(939) = a(85) + a(84) = 642 + 558.


MATHEMATICA

k = 8; Do[a[n] = 1, {n, k + 1}]; a[n_] := a[n] = a[n  k] + a[n  k  1]; Array[a, 76]
LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1}, 80] (* Harvey P. Dale, May 07 2015 *)


PROG

(PARI) a(n)=([0, 1, 0, 0, 0, 0, 0, 0, 0; 0, 0, 1, 0, 0, 0, 0, 0, 0; 0, 0, 0, 1, 0, 0, 0, 0, 0; 0, 0, 0, 0, 1, 0, 0, 0, 0; 0, 0, 0, 0, 0, 1, 0, 0, 0; 0, 0, 0, 0, 0, 0, 1, 0, 0; 0, 0, 0, 0, 0, 0, 0, 1, 0; 0, 0, 0, 0, 0, 0, 0, 0, 1; 1, 1, 0, 0, 0, 0, 0, 0, 0]^(n1)*[1; 1; 1; 1; 1; 1; 1; 1; 1])[1, 1] \\ Charles R Greathouse IV, Oct 03 2016


CROSSREFS

Cf. A000045, A000931, A079398, A103372A103381, A103386, A103396.
Sequence in context: A029241 A226749 A277090 * A189819 A145992 A045818
Adjacent sequences: A103373 A103374 A103375 * A103377 A103378 A103379


KEYWORD

nonn,easy


AUTHOR

Jonathan Vos Post, Feb 05 2005


EXTENSIONS

Edited by Ray Chandler, Feb 10 2005


STATUS

approved



