A015977 Two iterations of Reverse and Add are needed to reach a palindrome.

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

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

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Index entries for sequences related to Reverse and Add!

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

Cf. A002113, A065207.

Sequence in context: A125298 A037362 A102717 * A294239 A250050 A051052

Adjacent sequences: A015974 A015975 A015976 * A015978 A015979 A015980

Keyword

nonn,base

Author

Robert G. Wilson v

Status

approved