A256639 a(n) is the base-(-10) representation of a(n-1) read in base 10, starting from -1.

-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

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-François 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