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A015977 Two iterations of Reverse and Add are needed to reach a palindrome. 2
5, 6, 7, 8, 9, 19, 28, 37, 39, 46, 48, 49, 55, 57, 58, 64, 66, 67, 73, 75, 76, 82, 84, 85, 91, 93, 94, 109, 119, 129, 139, 149, 150, 151, 152, 153, 154, 159, 160, 161, 162, 163, 169, 170, 171, 172, 173, 179, 189, 208, 218, 219, 228, 229, 238, 239, 248 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
The number of iterations starts at 1, so palindromes (cf. A002113) are not excluded. The corresponding sequence excluding palindromes is A065207.
LINKS
MATHEMATICA
Select[Range[250], Boole[PalindromeQ/@Rest[NestList[#+IntegerReverse[#]&, #, 2]]] == {0, 1}&] (* Harvey P. Dale, May 11 2022 *)
PROG
(Python)
def ra(n): s = str(n); return int(s) + int(s[::-1])
def ispal(n): s = str(n); return s == s[::-1]
def aupto(limit):
alst = []
for k in range(limit+1):
k2 = ra(k)
if ispal(k2): continue
if ispal(ra(k2)): alst.append(k)
return alst
print(aupto(250)) # Michael S. Branicky, May 06 2021
CROSSREFS
Sequence in context: A125298 A037362 A102717 * A294239 A250050 A051052
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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Last modified July 25 01:41 EDT 2024. Contains 374585 sequences. (Running on oeis4.)