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.
%I A159000 #25 May 27 2025 10:34:32
%S A159000 3360,19440,35712,55800,120960,395808,451584,548640,628992,695520,
%T A159000 763344,3008768,3749760,5602320,17557344,46902240,55031040,119627904,
%U A159000 162496048,193933440,243855360,249793920,374473800,377677440,548402400
%N A159000 Numbers m such that m = s|t = phi(s)*sigma(t) for some numbers s and t, where "|" denotes concatenation.
%C A159000 A159001(n) gives the first part s of a(n).
%H A159000 Max Alekseyev, <a href="/A159000/b159000.txt">Table of n, a(n) for n = 1..51</a> (first 33 terms from Giovanni Resta)
%e A159000 3008768 = phi(3008)*sigma(768) so 3008768 is in the sequence.
%t A159000 ntnQ[n_]:=MemberQ[(EulerPhi[#[[1]]]DivisorSigma[1,#[[2]]])==n&/@ Table[FromDigits/@TakeDrop[IntegerDigits[n],i],{i,IntegerLength[ n]-1}],True]; Select[Range[55*10^7], ntnQ] (* The program uses the TakeDrop function from Mathematica version 10 *) (* The program takes a long time to run *) (* _Harvey P. Dale_, Jan 01 2016 *)
%o A159000 (PARI) isA159000(n)={my(m);for(i=1,#Str(n)-1,m=n%10^i;if(m,m=divrem(n,sigma(m));if(m[2]==0&eulerphi(n\10^i)==m[1],return(i))));0} /* _Charles R Greathouse IV_, Apr 28 2010 */
%Y A159000 Cf. A159001, A253824, A253825, A260144.
%K A159000 nonn,base
%O A159000 1,1
%A A159000 _Farideh Firoozbakht_, Jun 04 2009
%E A159000 Corrected (a(3), a(4), and a(11) missing), extended past a(12), and edited by _Charles R Greathouse IV_, Apr 28 2010