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A122189 Heptanacci numbers: each term is the sum of the preceding 7 terms, with a(0),...,a(6) = 0,0,0,0,0,0,1. 11
0, 0, 0, 0, 0, 0, 1, 1, 2, 4, 8, 16, 32, 64, 127, 253, 504, 1004, 2000, 3984, 7936, 15808, 31489, 62725, 124946, 248888, 495776, 987568, 1967200, 3918592, 7805695, 15548665, 30972384, 61695880, 122895984, 244804400, 487641600, 971364608, 1934923521 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,9

COMMENTS

See A066178 (essentially the same sequence) for more about the heptanacci numbers and other generalizations of the Fibonacci numbers (A000045).

LINKS

Robert Price, Table of n, a(n) for n = 0..1000

Martin Burtscher, Igor Szczyrba, Rafał Szczyrba, Analytic Representations of the n-anacci Constants and Generalizations Thereof, Journal of Integer Sequences, Vol. 18 (2015), Article 15.4.5.

F. T. Howard and Curtis Cooper, Some identities for r-Fibonacci numbers.

B. E. Merkel, Probabilities of Consecutive Events in Coin Flipping, Master's Thesis, Univ. Cincinatti, May 11 2011.

Index entries for linear recurrences with constant coefficients, signature (1,1,1,1,1,1,1).

FORMULA

G.f.: x^6/(1-x-x^2-x^3-x^4-x^5-x^6-x^7). - R. J. Mathar, Feb 13 2009

G.f.: sum_{n >= 0} x^(n+5) *[ product_{k = 1..n} (k + k*x + k*x^2 + k*x^3 + k*x^4 + k*x^5 + x^6)/(1 + k*x + k*x^2 + k*x^3 + k*x^4 + k*x^5 + k*x^6) ]. - Peter Bala, Jan 04 2015

Another form of the g.f.: f(z)=(z^6-z^7)/(1-2*z+z^8), then a(n) = sum_{i=0..floor((n-6)/8)} (-1)^i*binomial(n-6-7*i,i)*2^(n-6-8*i) - sum_{i=0..floor((n-7)/8)} (-1)^i*binomial(n-7-7*i,i)*2^(n-7-8*i) with sum_{i=m..n} alpha(i) = 0 for m>n. - Richard Choulet, Feb 22 2010

sum_{k=0..6*n} a(k+b)*A063265(n,k) = a(7*n+b), b>=0.

MAPLE

for n from 0 to 50 do k(n):=sum((-1)^i*binomial(n-6-7*i, i)*2^(n-6-8*i), i=0..floor((n-6)/8))-sum((-1)^i*binomial(n-7-7*i, i)*2^(n-7-8*i), i=0..floor((n-7)/8)):od:seq(k(n), n=0..50); a:=taylor((z^6-z^7)/(1-2*z+z^8), z=0, 51); for p from 0 to 50 do j(p):=coeff(a, z, p):od :seq(j(p), p=0..50); # Richard Choulet, Feb 22 2010

MATHEMATICA

a=0; b=0; c=0; d=0; e=0; f=0; g=1; lst={a, b, c, d, e, f, g}; Do[h=a+b+c+d+e+f+g; AppendTo[lst, h]; a=b; b=c; c=d; d=e; e=f; f=g; g=h, {n, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 30 2008 *)

LinearRecurrence[{1, 1, 1, 1, 1, 1, 1}, {0, 0, 0, 0, 0, 0, 1}, 50] (* Vladimir Joseph Stephan Orlovsky, May 25 2011 *)

a={0, 0, 0, 0, 0, 0, 1} For[n=7, n≤100, n++, sum=Plus@@a; Print[sum]; a=RotateLeft[a]; a[[7]]=sum] (* Robert Price, Dec 04 2014 *)

PROG

(PARI) a(n)=([0, 1, 0, 0, 0, 0, 0; 0, 0, 1, 0, 0, 0, 0; 0, 0, 0, 1, 0, 0, 0; 0, 0, 0, 0, 1, 0, 0; 0, 0, 0, 0, 0, 1, 0; 0, 0, 0, 0, 0, 0, 1; 1, 1, 1, 1, 1, 1, 1]^n*[0; 0; 0; 0; 0; 0; 1])[1, 1] \\ Charles R Greathouse IV, Jun 20 2015

CROSSREFS

Cf. A000045 (k=2, Fibonacci numbers), A000073 (k=3, tribonacci) A000078 (k=4, tetranacci) A001591 (k=5, pentanacci) A001592 (k=6, hexanacci), A122189 (k=7, heptanacci).

Cf. A066178, A000322, A248700.

Sequence in context: A062258 A239560 A066178 * A194630 A251672 A251747

Adjacent sequences:  A122186 A122187 A122188 * A122190 A122191 A122192

KEYWORD

nonn,easy

AUTHOR

Roger L. Bagula and Gary W. Adamson, Oct 18 2006

EXTENSIONS

Edited by N. J. A. Sloane, Nov 20 2007

Wrong Binet-type formula removed by R. J. Mathar, Feb 13 2009

STATUS

approved

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Last modified August 29 20:15 EDT 2015. Contains 261200 sequences.