login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A099954 Numbers n such that Fibonacci(n) is a semiprime and its reversal is a different semiprime. 1
19, 22, 31, 41, 59, 107, 193, 199, 227, 467 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(11) > 1000. [Donovan Johnson, Jun 06 2009]

LINKS

Table of n, a(n) for n=1..10.

EXAMPLE

F(19) = 4181 = 37 * 113, Reverse[F(19)] = 1814 = 2 * 907.

MAPLE

with(combinat): with(numtheory): rev:=proc(n) local nn: nn:=convert(n, base, 10): add(nn[nops(nn)+1-j]*10^(j-1), j=1..nops(nn)) end: a:=proc(n): if rev(fibonacci(n))<>fibonacci(n) and bigomega(fibonacci(n))=2 and bigomega(rev(fibonacci(n)))=2 then n else fi end: seq(a(n), n=1..200); # Emeric Deutsch, Jul 26 2006

MATHEMATICA

fspQ[n_]:=Module[{f=Fibonacci[n]}, f!=IntegerReverse[f]&&PrimeOmega[f] == PrimeOmega[IntegerReverse[f]]==2]; Select[Range[470], fspQ] (* Harvey P. Dale, Jul 24 2016 *)

CROSSREFS

Intersection of A000045 and A097393.

Sequence in context: A113868 A056025 A284670 * A335347 A050955 A303299

Adjacent sequences:  A099951 A099952 A099953 * A099955 A099956 A099957

KEYWORD

nonn,base,more

AUTHOR

Jonathan Vos Post and G. L. Honaker, Jr., Nov 13 2004

EXTENSIONS

More terms from Emeric Deutsch, Jul 26 2006

a(10) from Donovan Johnson, Jun 06 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 7 15:02 EDT 2021. Contains 343650 sequences. (Running on oeis4.)