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.

A080651 Numbers n such that n and Fibonacci(n) have the same number of divisors.

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%I A080651 #18 Dec 31 2019 20:04:21
%S A080651 1,3,5,6,7,8,10,11,13,14,17,22,23,26,29,34,43,47,83,94,131,137,359,
%T A080651 431,433,449,509,569,571,2971,4723,5387,9311,9677,14431
%N A080651 Numbers n such that n and Fibonacci(n) have the same number of divisors.
%C A080651 Except for A001605(2) = 4, all terms of A001605 are terms of this sequence. - _Chai Wah Wu_, Dec 30 2019
%H A080651 Blair Kelly, <a href="http://mersennus.net/fibonacci/">Fibonacci and Lucas Factorizations</a>.
%F A080651 a(n) = A001605(n-8) for n >= 21 (conjectured). - _Chai Wah Wu_, Dec 30 2019
%t A080651 Select[Range[2*10^2], DivisorSigma[0, Fibonacci[ # ]] == DivisorSigma[0, # ] &]
%o A080651 (PARI) isok(n) = numdiv(n) == numdiv(fibonacci(n)); \\ _Michel Marcus_, Feb 25 2016
%Y A080651 Cf. A001605, A063375.
%K A080651 nonn,more
%O A080651 1,2
%A A080651 _Joseph L. Pe_, Feb 28 2003
%E A080651 More terms from _Ryan Propper_, May 31 2006
%E A080651 a(30)-a(34) from _Chai Wah Wu_, Dec 30 2019
%E A080651 a(35) from _Chai Wah Wu_, Dec 31 2019