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 A085928 a(1) = 1, a(2) = 2, then the absolute difference of the concatenation of two previous terms and its digit reversal. 0
 1, 2, 9, 63, 594, 14058, 25627437, 5941439657604, 150482558208133815048, 2463743660424402357955859435526447, 5941429767504259381561776919813218438160375943419757604, 16038354830713282603922637536703240576965473072533033395669335536367159371668297243716038 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is a multiple of 99 for n > 4. Conjecture: The sequence has finitely many nonzero terms. (This would happen when the concatenation of two successive terms becomes a palindrome and the next term is 0.) LINKS EXAMPLE a(1) = 1, a(2) = 2, a(3) = |12-21| = 9, a(4) = |29-92| = 63, a(5) = |963-369| = 594, a(6) = |63594 - 49536| = 14058, a(7) = |59418018 - 81081495| = 21663477, ... MATHEMATICA nxt[{a_, b_}]:=Module[{id=Join[IntegerDigits[a], IntegerDigits[b]]}, {b, Abs[ FromDigits[ id]- FromDigits[Reverse[id]]]}]; Transpose[NestList[nxt, {1, 2}, 12]][[1]] (* Harvey P. Dale, Nov 30 2014 *) CROSSREFS Sequence in context: A166886 A212413 A003577 * A130169 A218672 A253109 Adjacent sequences:  A085925 A085926 A085927 * A085929 A085930 A085931 KEYWORD base,nonn AUTHOR Amarnath Murthy and Jason Earls, Jul 13 2003 EXTENSIONS Corrected and extended by Mark Hudson (mrmarkhudson(AT)hotmail.com), Jul 23 2004 More terms from David Wasserman, Feb 11 2005 One more term (a(12)) from Harvey P. Dale, Nov 30 2014 STATUS approved

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Last modified August 5 22:09 EDT 2020. Contains 336214 sequences. (Running on oeis4.)