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

Author

Gerald Hillier, Apr 23 2015

Keywords

• sign
• base

Comments

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

Crossrefs

Cf. A039723.

Programs

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 *)