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A195906 A periodic sequence. 1
22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6, 54, 27, 22, 11, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Start with a number. If the number is a single-digit number, multiply it by 9. If the number is a multidigit even number, halve it. If it is a multidigit odd number, subtract 5. Continuing this process leads to a repeating cycle of 5 terms.

There are two different 5-term cycles: 5,45,40,20,10 and 6,54,27,22,11. First corresponds to a(1)=5, second to a(1) = all other positive digits. - Zak Seidov, Sep 25 2011

LINKS

Muniru A Asiru, Table of n, a(n) for n = 1..2000

T. Trotter, Beyond Ulam [Cached copy; c.f. Terrel Trotter's user page]

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,1).

FORMULA

G.f.: x*(22 + 11*x + 6*x^2 + 54*x^3 + 27*x^4)/(1 - x^5). - Chai Wah Wu, Jun 04 2016

MAPLE

seq(coeff(series(x*(22+11*x+6*x^2+54*x^3+27*x^4)/(1-x^5), x, n+1), x, n), n = 1 .. 80); # Muniru A Asiru, Dec 08 2018

MATHEMATICA

f[n_] := If[n < 10, 9n, If[EvenQ[n], n/2, n - 5]]; NestList[f, 22, 100]  (* Amiram Eldar, Dec 08 2018 *)

LinearRecurrence[{0, 0, 0, 0, 1}, {22, 11, 6, 54, 27}, 80] (* Vincenzo Librandi, Dec 09 2018 *)

PROG

(MAGMA) &cat [[22, 11, 6, 54, 27]^^20]; // Vincenzo Librandi, Dec 09 2018

CROSSREFS

Sequence in context: A196103 A196100 A317870 * A033342 A102612 A040465

Adjacent sequences:  A195903 A195904 A195905 * A195907 A195908 A195909

KEYWORD

nonn,base,easy

AUTHOR

Kausthub Gudipati, Sep 25 2011

STATUS

approved

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Last modified August 22 11:59 EDT 2019. Contains 326177 sequences. (Running on oeis4.)