A075685 - OEIS

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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 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,8`
	COMMENTS	`Base 4 analogue of A033665 (base 10) and A066057 (base 2). For values of n such that presumably a(n) = -1 see A075420.`
	LINKS	`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: A060763 A131576 A100073 * A037906 A120936 A173432` `Adjacent sequences: A075682 A075683 A075684 * A075686 A075687 A075688`
	KEYWORD	`base,nonn`
	AUTHOR	`Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Sep 24 2002`

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Last modified February 17 16:39 EST 2012. Contains 206058 sequences.