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Lucas numbers for which the product of the digits is a Fibonacci number.
2

%I #14 Mar 14 2016 03:52:38

%S 1,3,11,18,2207,39603,64079,103682,439204,710647,1860498,3010349,

%T 4870847,12752043,20633239,54018521,87403803,370248451,599074578,

%U 969323029,1568397607,2537720636,4106118243,10749957122,17393796001

%N Lucas numbers for which the product of the digits is a Fibonacci number.

%C A000204 INTERSECT A011540 is a subsequence. As a consequence of Carmichael's theorem, the product of the digits of terms in the sequence must be in the set {0, 1, 2, 3, 5, 8, 21, 144} and if a term is zeroless (A052382), then at most 6 digits are not equal to 1. Conjecture: all terms > 18 have a 0 digit, i.e. is a member of A011540. - _Chai Wah Wu_, Mar 12 2016

%H Chai Wah Wu, <a href="/A117769/b117769.txt">Table of n, a(n) for n = 1..1000</a>

%e 18 is in the sequence because (1)it is a Lucas number and (2)the product of its digits 1*8=8 is a Fibonacci number.

%o (Python)

%o from operator import mul

%o from functools import reduce

%o A117769_list, a, b = [], 2, 1

%o for i in range(10**3):

%o if reduce(mul,(int(d) for d in str(b))) in (0,1,2,3,5,8,21,144):

%o A117769_list.append(b)

%o a, b = b, a+b # _Chai Wah Wu_, Mar 13 2016

%Y Cf. A000045, A000204, A117770.

%K base,nonn

%O 1,2

%A Luc Stevens (lms022(AT)yahoo.com), Apr 15 2006

%E a(24) corrected and offset changed by _Chai Wah Wu_, Mar 12 2016

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Last modified September 23 16:16 EDT 2024. Contains 376178 sequences. (Running on oeis4.)