A188650 Fixed points of A188649: numbers divisible by the reverse of all their divisors.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 20, 22, 33, 40, 44, 55, 66, 77, 88, 99, 101, 110, 121, 131, 151, 181, 191, 202, 220, 242, 262, 303, 313, 353, 363, 373, 383, 393, 404, 440, 484, 505, 606, 626, 707, 727, 757, 787, 797, 808, 909, 919, 929, 939, 1010, 1111, 1331, 1441, 1661, 1991, 2020, 2222, 2662, 2882, 3333, 3443, 3883, 3993, 4040, 4444, 5555, 6666, 6886, 7777, 7997, 8888

Offset

1,2

Comments

A188649(a(n)) = a(n);

A002385 and A046376 are subsequences; subsequence of A002113.

Links

Michael S. Branicky, Table of n, a(n) for n = 1..10700

Prog

(Haskell)
import Data.List (elemIndices)
a188650 n = a188650_list !! (n-1)
a188650_list =
   map succ $ elemIndices 0 $ zipWith (-) [1..] $ map a188649 [1..]
(PARI) rev(n:int, B=10)=my(m=n%B); n\=B; while(n>0, m=m*B+n%B; n\=B); m
is(n)=fordiv(n, d, if(n%rev(d), return(0))); 1 \\ Charles R Greathouse IV, Jul 14 2011
(Python)
from math import lcm
from sympy import divisors
def ok(n): return n == lcm(*(int(str(d)[::-1]) for d in divisors(n)))
print([k for k in range(1, 10000) if ok(k)]) # Michael S. Branicky, Sep 30 2022

Crossrefs

Sequence in context: A114801 A114802 A055933 * A132578 A101318 A337925

Adjacent sequences: A188647 A188648 A188649 * A188651 A188652 A188653

Keyword

nonn,base

Author

Reinhard Zumkeller, Apr 11 2011

Status

approved