cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A087093 Numbers that have the same number of divisors as their digit reversal, but with different prime signatures.

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%I A087093 #19 Dec 30 2020 04:11:27
%S A087093 24,42,264,288,462,658,856,882,1071,1128,1314,1464,1701,2058,2130,
%T A087093 2132,2312,2324,2424,2510,2590,2616,2664,2744,2765,2782,2786,2872,
%U A087093 2904,2938,2975,3159,3194,4010,4090,4092,4094,4125,4131,4136,4168,4184,4220,4228
%N A087093 Numbers that have the same number of divisors as their digit reversal, but with different prime signatures.
%C A087093 Terms in A062895 but not in A085869.
%H A087093 Amiram Eldar, <a href="/A087093/b087093.txt">Table of n, a(n) for n = 1..10000</a>
%e A087093 24 and 42 are members as 24 and 42 each have 8 divisors but with different prime signatures.
%t A087093 psQ[n_]:=Sort[Transpose[FactorInteger[n]][[2]]]!=Sort[Transpose[ FactorInteger[FromDigits[Reverse[IntegerDigits[n]]]]][[2]]];ndQ[n_]:= DivisorSigma[0,n]==DivisorSigma[0,FromDigits[Reverse[ IntegerDigits[ n]]]]; Select[Range[5000],psQ[#]&&ndQ[#]&] (* _Harvey P. Dale_, Nov 11 2011 *)
%Y A087093 Cf. A000005, A062895, A085869, A085870.
%K A087093 nonn,base
%O A087093 1,1
%A A087093 _Ray Chandler_, Aug 09 2003