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%I #25 Jul 24 2015 02:26:23
%S 124,2352,2604,6804,15240,63180,225302,632400,1531152,2537040,4592588,
%T 7160400,7603680,26100144,26378352,31492032,33747840,49447728,
%U 88385040,104941200,162496048,175600040,197499456,403242624,483741216,797091840,2077442640,2942021520,4045874976,4828299840
%N Numbers n = concat(s,t) such that n = sigma(s*t), where sigma(x) is the sum of the divisors of x.
%e 124 = concat(12,4) and sigma(12*4) = sigma(48) = 124.
%e 2352 = concat(23,52) and sigma(23*52) = sigma(1196) = 2352.
%p with(numtheory); P:=proc(q) local a,b,i,n,p; for n from 1 to q do
%p for i from 1 to ilog10(n) do a:=trunc(n/10^i); b:=n-a*10^i;
%p if sigma(a*b)=n then print(n); break; fi; od; od; end: P(10^9);
%o (PARI) isok(n) = {len = #Str(n); for (k=1, len-1, na = n\10^k; nb = n % 10^k; if (nb && (n == sigma(na*nb)), return (1)); ); } \\ _Michel Marcus_, Jul 17 2015
%o (Python)
%o from sympy import divisor_sigma
%o A260097_list= []
%o for n in range(11,10**6):
%o ....s = str(n)
%o ....for l in range(1,len(s)):
%o ........m = int(s[:l])*int(s[l:])
%o ........if m > 0 and n == divisor_sigma(m):
%o ............A260097_list.append(n)
%o ............break # _Chai Wah Wu_, Jul 18 2015
%Y Cf. A000203, A253824, A253825.
%K nonn,base
%O 1,1
%A _Paolo P. Lava_, Jul 16 2015
%E a(14)-a(15) from _Chai Wah Wu_, Jul 18 2015
%E a(16)-a(28) from _Lars Blomberg_, Jul 21 2015
%E a(29)-a(30) from _Giovanni Resta_, Jul 24 2015
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