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A071683 Nonprimes which are the average of two consecutive Fibonacci numbers. 0

%I

%S 1,4,72,305,1292,5473,23184,98209,416020,1762289,7465176,31622993,

%T 133957148,567451585,2403763488,10182505537,43133785636,182717648081,

%U 774004377960,3278735159921,13888945017644,58834515230497

%N Nonprimes which are the average of two consecutive Fibonacci numbers.

%C Prove that 17 is the only prime which is the average of two consecutive Fibonacci numbers.

%t f[n_] := Fibonacci[n]; a = Select[ Range[70], IntegerQ[(f[ # ] + f[ # + 1])/2] && !PrimeQ[(f[ # ] + f[ # + 1])/2] &]; (f[a] + f[a + 1])/2

%Y Cf. A018252, A000045.

%K nonn

%O 1,2

%A _G. L. Honaker, Jr._, Jun 22 2002

%E Edited by _Robert G. Wilson v_, Jun 27 2002

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Last modified October 16 20:55 EDT 2019. Contains 328103 sequences. (Running on oeis4.)