cp's OEIS Frontend

The sequence starts with 1999290307891606810 and continues for another 125 terms (none previously reported, including the first term) each turning into a 119-digit palindrome after 261 steps until the sequence ends with 1999291987030606810. The distance between successive terms in the reported sequence has 9000000 as the greatest common divisor. No further numbers beyond 1999291987030606810 belonging to the same sequence are known, discovered or reported. Moreover, 1999291987030606810 is currently the largest discovered "most delayed palindrome". The sequence was found empirically using computer modeling algorithms.

It is only a conjecture that there are no further terms. - N. J. A. Sloane, Jan 24 2017

RECORDS transform of A075685. - Base-4 analog of A065198 (base 10) and A066144 (base 2). Integers like 290, for which a palindrome is (presumably) never reached (cf. A075420), are of course disregarded. A075687 gives the corresponding records.

1999291987030606810 is the largest of the 126 presently known numbers that require exactly 261 steps to turn into a palindrome (see A281508). It is also the largest discovered "most delayed palindrome". The sequence reaches a 119-digit palindrome after 261 steps (see b-file). The number was obtained empirically using computer algorithms and was not reported before.

It is conjectured that if a Reverse and Add! trajectory reaches a palindrome, it will be reached in relatively few steps, or otherwise it will never reach a palindrome. - A.H.M. Smeets, May 30 2019

It is conjectured that if a Reverse and Add! trajectory reaches a palindrome, it will be reached in relatively few steps, or otherwise it will never reach a palindrome.

For all n, all numbers m < A306599(n) will reach a palindrome within a(n) Reverse and Add! steps, or otherwise it is conjectured never to reach a palindrome.

RECORDS transform of A077402. - Base-3 analog of A066144 (base 2), A075686 (base 4) and A065198 (base 10). Integers like 103, for which a palindrome is (presumably) never reached (cf. A077404), are of course disregarded. A077407 gives the corresponding records.

The sequence starts with 1003062289999939142 (the 19-digit number discovered by Vaughn Suite on Mar 19 2006) and continues for another 430079 terms (none previously reported) each turning into a 119-digit palindrome after 260 steps until the sequence ends with 3419399999822603000 (see a-file). No further numbers beyond 3419399999822603000 belonging to the same sequence exist. The sequence was predicted theoretically and found empirically using computer modeling algorithms. For the first 100 terms of the sequence see b-file.

Records in A323976.

Similar to the number of steps needed to reach a palindrome in the Reverse and Add! trajectories (see A065198 and A065199), the number of steps needed for a Lychrel number to reach the trajectory of its seed is relatively small.

Similar to the number of steps needed to reach a palindrome in the Reverse and Add! trajectories (see A065198 and A065199), the number of steps needed for a Lychrel number to reach the trajectory of its seed is relatively small.