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A256639 a(n) is the base-(-10) representation of a(n-1) read in base 10, starting from -1. 0
-1, 19, 199, 219, 399, 419, 599, 619, 799, 819, 999, 19019, 21199, 39219, 41399, 59419, 61599, 79619, 81799, 99819, 1901999, 2118019, 3922199, 4138219, 5942399, 6158419, 7962599, 8178619, 9982799, 190198819, 211802999, 392217019, 413823199, 594237219, 615843399, 796257419, 817863599, 998277619, 19019883799 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Decimal -1 in negadecimal is 19, decimal 19 in negadecimal is 199, decimal 199 in negadecimal is 219, ....

LINKS

Table of n, a(n) for n=1..39.

MATHEMATICA

negaDecimal[n_] := Mod[NestWhileList[Function[k, (Mod[k, 10]-k)/10], n, # != 0&], 10] // Reverse // Rest // FromDigits; a[1] = -1; a[n_] := a[n] = negaDecimal[a[n-1]]; Array[a, 40] (* Jean-Fran├žois Alcover, Nov 23 2016 *)

PROG

(HP 49G calculator) Given a(n) the program produces a(n+1).

::

  CK1&Dispatch

  # FF

  ::

    Z10_

    ZINT -10

    FPTR2 ^2LAMBIND

    NULL$SWAP

    BEGIN

    1GETLAM

    FPTR2 ^IDIV2

    FPTR2 ^DupQIsZero?

    ?SKIP

    ::

      2GETLAM

      FPTR2 ^RADDext

      SWAP

      Z1_

      FPTR2 ^RADDext

      SWAP

    ;

    FPTR2 ^Z>S

    ROT

    &$SWAP

    FPTR2 ^DupQIsZero?

    UNTIL

    ABND

    DROP

    FPTR2 ^S>Z

  ;

;

CROSSREFS

Cf. A039723.

Sequence in context: A210339 A097445 A238697 * A058370 A230012 A164890

Adjacent sequences:  A256636 A256637 A256638 * A256640 A256641 A256642

KEYWORD

sign,base

AUTHOR

Gerald Hillier, Apr 23 2015

STATUS

approved

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Last modified October 20 12:47 EDT 2019. Contains 328257 sequences. (Running on oeis4.)