|
%I #17 Nov 20 2019 07:52:08
%S 1,2,3,5,7,11,13,17,23,31,37,53,71,73,113,131,137,173,197,311,313,317,
%T 373,797,1373,1997,3137,3797,7331,73331,739397
%N Numbers such that every prefix and suffix is 1 or a prime.
%C Last term is 739397 (confirmed by _David W. Wilson_).
%C Intersection of A012883 and A143390. [_Reinhard Zumkeller_, Aug 13 2008]
%t prQ[n_] := n == 1 || PrimeQ[n];
%t 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, #]&]];
%t {1}~Join~Select[Prime@Range[60000], okQ] (* _Jean-François Alcover_, Nov 20 2019 *)
%Y Cf. A068669.
%K nonn,fini,full,nice,base
%O 1,2
%A Larry Calmer (larry(AT)wri.com), _Simon Plouffe_
|
