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A071683
Nonprimes which are the average of two consecutive Fibonacci numbers.
0
1, 4, 72, 305, 1292, 5473, 23184, 98209, 416020, 1762289, 7465176, 31622993, 133957148, 567451585, 2403763488, 10182505537, 43133785636, 182717648081, 774004377960, 3278735159921, 13888945017644, 58834515230497
OFFSET
1,2
COMMENTS
Prove that 17 is the only prime which is the average of two consecutive Fibonacci numbers.
MATHEMATICA
f[n_] := Fibonacci[n]; a = Select[ Range[70], IntegerQ[(f[ # ] + f[ # + 1])/2] && !PrimeQ[(f[ # ] + f[ # + 1])/2] &]; (f[a] + f[a + 1])/2
CROSSREFS
Sequence in context: A203537 A095385 A375251 * A192826 A190398 A003752
KEYWORD
nonn
AUTHOR
G. L. Honaker, Jr., Jun 22 2002
EXTENSIONS
Edited by Robert G. Wilson v, Jun 27 2002
STATUS
approved