A015979 Three iterations of Reverse and Add are needed to reach a palindrome.

59, 68, 77, 86, 95, 155, 156, 157, 158, 164, 165, 168, 178, 180, 184, 185, 186, 194, 199, 249, 254, 255, 256, 257, 263, 264, 267, 277, 283, 284, 285, 293, 298, 299, 348, 349, 353, 354, 355, 356, 362, 363, 366, 376, 382, 383, 384, 389, 392, 397

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn
• base

Comments

The number of iterations starts at 1, so palindromes (cf. A002113) are not excluded. The corresponding sequence excluding palindromes is A065208.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to Reverse and Add!

Crossrefs

Cf. A002113, A065208.

Programs

Maple

filter:= proc(n,t) local x, d, m, L, i;
  x:= n;
  L:= convert(x,base,10);
  for i from 1 to t do
    d:= nops(L);
    x:= add(L[i]*(10^(i-1) + 10^(d-i)),i=1..d);
    L:= convert(x,base,10);
    if L = ListTools:-Reverse(L) then return (i=t) fi;
  od;
  false
end proc:
select(filter, [$1..1000], 3); # Robert Israel, Aug 26 2024

Extensions

Offset corrected by Robert Israel, Aug 26 2024