A075685 Reverse and Add! carried out in base 4; number of steps needed to reach a palindrome, or -1 if no palindrome is ever reached.

0, 0, 0, 0, 1, 0, 1, 2, 1, 1, 0, 1, 1, 2, 1, 0, 1, 0, 1, 2, 1, 0, 1, 2, 2, 0, 3, 2, 4, 0, 4, 3, 1, 1, 0, 1, 1, 1, 0, 4, 2, 3, 0, 2, 3, 4, 0, 4, 1, 2, 1, 0, 1, 2, 4, 0, 3, 2, 2, 0, 4, 3, 4, 0, 1, 0, 1, 2, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 2, 1, 1, 1, 2, 1, 0, 1, 3, 1, 1, 1, 2, 2, 3, 3, 2, 1, 1, 1, 3, 1, 1, 1, 2, 2

Offset

0,8

Comments

Base-4 analog of A033665 (base 10) and A066057 (base 2). For values of n such that presumably a(n) = -1 see A075420.

Links

Table of n, a(n) for n=0..104.

Index entries for sequences related to Reverse and Add!

Example

26 (decimal) = 122 -> 122 + 221 = 1003 -> 1003 + 3001 = 10010 -> 10010 + 01001 = 11011 (palindrome) = 325 (decimal) requires 3 steps, so a(26) = 3.

Prog

(ARIBAS) m := 105; stop := 1000; for n := 0 to m do c := 0; k := n; v := -1; while c < stop do a := k; rev := 0; while a > 0 do rev := 4*rev + (a mod 4); a := a div 4; end; if k = rev then v := c; c := stop; else inc(c); k := k + rev; end; end; write(v, " "); end; .

Crossrefs

Cf. A014192, A033665, A066057, A075420.

Sequence in context: A100073 A257988 A340379 * A037906 A319394 A278347

Adjacent sequences: A075682 A075683 A075684 * A075686 A075687 A075688

Keyword

base,nonn

Author

Klaus Brockhaus, Sep 24 2002

Status

approved