cp's OEIS Frontend

A062895 Numbers k for which d(k) = d(R(k)), where R(k) is the reversal of k and d(k) is the number of divisors of k.

%I A062895 #30 May 13 2025 18:05:50
%S A062895 1,2,3,4,5,6,7,8,9,11,13,15,17,22,24,26,31,33,37,39,42,44,51,55,58,62,
%T A062895 66,71,73,77,79,85,88,93,97,99,101,107,111,113,115,117,121,122,123,
%U A062895 129,131,141,143,149,151,155,157,158,159,161,165,167,169,171,177,178,179
%N A062895 Numbers k for which d(k) = d(R(k)), where R(k) is the reversal of k and d(k) is the number of divisors of k.
%C A062895 The sequence s of numbers k for which R(d(k)) = d(R(k)) first differs at s(80) = 262 while a(80) = 252. - _Mohammed Yaseen_, Mar 24 2023
%H A062895 Mohammed Yaseen, <a href="/A062895/b062895.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Harry J. Smith)
%e A062895 d(24) = 8 and also d(42) = 8, hence both are members.
%t A062895 Select[Range[180],DivisorSigma[0,#]==DivisorSigma[0,FromDigits[Reverse[IntegerDigits[#]]]] &] (* _Jayanta Basu_, May 17 2013 *)
%o A062895 (PARI) { n=0; for (m=1, 10^9, x=m; r=0; while (x>0, d=x-10*(x\10); x\=10; r=r*10 + d); if (numdiv(m) == numdiv(r), write("b062895.txt", n++, " ", m); if (n==1000, break)) ) } \\ _Harry J. Smith_, Aug 12 2009
%o A062895 (PARI) isok(k) = numdiv(fromdigits(Vecrev(digits(k)))) == numdiv(k); \\ _Michel Marcus_, Jul 06 2021
%o A062895 (Python)
%o A062895 from sympy import divisor_count as d
%o A062895 def ok(n): return d(n) == d(int(str(n)[::-1]))
%o A062895 print([k for k in range(1, 180) if ok(k)]) # _Michael S. Branicky_, Mar 24 2023
%Y A062895 Cf. A000005 (d), A004086 (R), A002113 (palindromes: subsequence).
%Y A062895 Cf. A350867 (subsequence of non-palindromic terms), A085329 (similar with sigma).
%K A062895 base,nonn,easy
%O A062895 1,2
%A A062895 _Amarnath Murthy_, Jun 30 2001
%E A062895 Corrected and extended by _Vladeta Jovovic_, Jun 30 2001