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A009944 Left-right/right-left numbers: n = pq such that n=q_reversed*p_reversed.

%I A009944 #27 Apr 13 2024 17:26:12
%S A009944 126,153,688,187029,223524,267034,1574253,10013323,10353244,36528975,
%T A009944 109019911,116257833,1958249722,2285044524,2996225824,6264507888,
%U A009944 10544814252,15742574253,31951523916,35497206387,62967699976,94691579179,182738252812,187021087029
%N A009944 Left-right/right-left numbers: n = pq such that n=q_reversed*p_reversed.
%C A009944 The decimal expansion of n is p followed by q, and n is also the product of R(p)*R(q), where R reverses the order of the digits. - _N. J. A. Sloane_, May 22 2016
%C A009944 A subset of A179482; only two factors permitted. - _Adam Kertesz_, Aug 07 2010
%C A009944 The sequence is infinite, since it contains at least 3 infinite subsequences, namely b(n) = 3*(88810 + 2099*10^(6*n))/33670 = 187029, 187021087029,... c(n) = 11011*(1 + 100^(1 + 2*n))/101 = 109019911, 1090198019911,... and d(n) = 3*(53*10000^n - 14900)/10100 = 153, 1574253,... - _Giovanni Resta_, Mar 17 2013
%H A009944 Giovanni Resta, <a href="/A009944/b009944.txt">Table of n, a(n) for n = 1..30</a>
%e A009944 E.g. 223524 = 42 * 5322.
%t A009944 Reap[For[n = 1, n < 2*10^8, n++, For[dd = IntegerDigits[n] // Reverse; k = 1, k <= Length[dd] - 1, k++, If[n == FromDigits[dd[[1 ;; k]]]*FromDigits[ dd[[k + 1 ;; -1]]], Print[n]; Sow[n]; Break[]]]]][[2, 1]] (* _Jean-François Alcover_, May 22 2016 *)
%o A009944 (Python)
%o A009944 from sympy import divisors
%o A009944 def ok(n):
%o A009944     if n%10==0: return False
%o A009944     t = str(n)[::-1]
%o A009944     return any(t==str(d)+str(n//d) for d in divisors(n, generator=True))
%o A009944 print([k for k in range(10**6) if ok(k)]) # _Michael S. Branicky_, Apr 13 2024
%Y A009944 Cf. A004086, A179482.
%K A009944 base,nonn,nice
%O A009944 1,1
%A A009944 Mario Velucchi (mathchess(AT)velucchi.it)
%E A009944 _David W. Wilson_ has verified that all terms shown are correct, Sep 28 2000