%I #7 Sep 25 2017 07:51:03

%S 0,1,5,8,21,4181

%N Fibonacci numbers that are also generalized octagonal numbers.

%C Intersection of A000045 and A001082.

%C These are all the terms, as confirmed by Tengely (2009).

%C All (generalized) g-gonal numbers in Lucas sequences up to g=20 have been determined, see Tengely (2009).

%H Szabolcs Tengely, <a href="http://shrek.unideb.hu/~tengely/G-gonal-FQ.pdf">Finding g-gonal numbers in recurrence sequences</a>, Fibonacci Quarterly, vol.46/47, no.3, pp.235-240, (2009).

%Y Cf. A000045, A001082.

%Y Cf. A039595 (triangular Fibonacci numbers).

%K nonn,easy,fini,full

%O 0,3

%A _Tomohiro Yamada_, Sep 25 2017