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A012884 Numbers such that every prefix and suffix is 1 or a prime. 5
1, 2, 3, 5, 7, 11, 13, 17, 23, 31, 37, 53, 71, 73, 113, 131, 137, 173, 197, 311, 313, 317, 373, 797, 1373, 1997, 3137, 3797, 7331, 73331, 739397 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Last term is 739397 (confirmed by David W. Wilson).

Intersection of A012883 and A143390. [Reinhard Zumkeller, Aug 13 2008]

LINKS

Table of n, a(n) for n=1..31.

MATHEMATICA

prQ[n_] := n == 1 || PrimeQ[n];

okQ[n_] := Module[{dd, nd}, dd = IntegerDigits[n]; nd = Length[dd]; AllTrue[Range[nd], prQ@ FromDigits@ Take[dd, #]&] && AllTrue[Range[nd-1], prQ@ FromDigits@ Drop[dd, #]&]];

{1}~Join~Select[Prime@Range[60000], okQ] (* Jean-François Alcover, Nov 20 2019 *)

CROSSREFS

Cf. A068669.

Sequence in context: A036962 A160337 A190222 * A068669 A316412 A100553

Adjacent sequences:  A012881 A012882 A012883 * A012885 A012886 A012887

KEYWORD

nonn,fini,full,nice,base

AUTHOR

Larry Calmer (larry(AT)wri.com), Simon Plouffe

STATUS

approved

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Last modified August 11 06:20 EDT 2020. Contains 336422 sequences. (Running on oeis4.)