A073956 Palindromes whose sum of anti-divisors is palindromic.

1, 2, 3, 4, 5, 6, 8, 9, 242, 252, 323, 434, 727, 4774, 32223, 42024, 43234, 46864, 64946, 70607, 4855584, 4942494, 6125216, 6265626, 149939941, 188737881, 241383142, 389181983, 470212074, 27685458672, 42685658624, 45625352654, 61039793016

Offset: 1

Author

Jason Earls, Sep 03 2002

Keywords

• base
• nonn

Comments

See A066272 for definition of anti-divisor.

Links

• Sean A. Irvine, Table of n, a(n) for n = 1..45

Crossrefs

Cf. A002113 (palindromes), A066272, A066417.

Programs

Python

from itertools import chain
def is_palindrome(x):
    return x == x[::-1]
A073956 = sorted([n for n in chain(map(lambda x:int(str(x)+str(x)[::-1]),range(1,10**2)),map(lambda x:int(str(x)+str(x)[-2::-1]), range(1,10**3))) if is_palindrome(str(int(sum([d for d in range(2,n,2) if n%d and not 2*n%d]))+int(sum([d for d in range(3,n,2) if n%d and 2*n%d in [d-1,1]]))))]) # Chai Wah Wu, Aug 09 2014

Extensions

a(21)-a(33) from Donovan Johnson, Mar 30 2010