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A116888 Primes p that remain prime through 4 iterations of the function f(p) = p^2 + 4. 3
306167, 48639197, 64695713, 68252687, 87788237, 87813293, 160486967, 255974437, 283032247, 324609913, 361705873, 417684523, 449364197, 451995587, 454052213, 466037563, 536504713, 574746467, 596095613 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..19.

EXAMPLE

p = 306167, f(p) = 93738231893, f(f(p)) = 8786856118425842363453, f(f(f(p))) = 77208840445917661077402487029419236950083213 and the 88-digit number f(f(f(f(p)))) are all prime numbers.

MATHEMATICA

Select[Prime[Range[9! ]], PrimeQ[ #^2+4]&&PrimeQ[(#^2+4)^2+4]&&PrimeQ[((#^2+4)^2+4)^2+4]&&PrimeQ[(((#^2+4)^2+4)^2+4)^2+4]&] (* Vladimir Joseph Stephan Orlovsky, Feb 26 2010 *)

CROSSREFS

Cf. A062324, A116886, A116887, A116889.

Sequence in context: A053849 A227780 A237950 * A270764 A236818 A234188

Adjacent sequences:  A116885 A116886 A116887 * A116889 A116890 A116891

KEYWORD

nonn

AUTHOR

Giovanni Resta, Feb 27 2006

STATUS

approved

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Last modified October 6 16:34 EDT 2022. Contains 357270 sequences. (Running on oeis4.)