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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
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.)
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: A377843 A212413 A003577 * A130169 A218672 A253109
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