%I A071119
%S A071119 2,3,5,7,131,151,353,373,727,757,929,11311,31513,33533,37273,37573,
%T A071119 39293,71317,93739,97579,1335331,3315133,3392933,7392937,9375739,
%U A071119 373929373,733929337
%N A071119 Palindromic primes in which deleting the outside pair of digits yields 
               a prime at every stage until finally a single-digit prime is obtained.
%D A071119 J.-P. Delahaye, "Pour la science", (French edition of Scientific American), 
               Juin 2002, p. 99.
%D A071119 G. L. Honaker, Jr. and C. Caldwell, Palindromic prime pyramids, J. Recreational 
               Mathematics, vol. 30.3, pp. 169-176, 1999-2000.
%H A071119 G. L. Honaker, Jr. and C. K. Caldwell, <a href="http://www.utm.edu/staff/
               caldwell/preprints/JRM_prime_pyramids.pdf">Palindromic Prime Pyramids</
               a>
%H A071119 G. L. Honaker, Jr. and C. K. Caldwell, <a href="http://www.utm.edu/staff/
               caldwell/supplements">Supplement to "Palindromic Prime Pyramids"</
               a>
%H A071119 I. Peterson, MathTrek, <a href="http://www.maa.org/mathland/mathtrek_08_29_05.html">
               Primes, Palindromes and Pyramids</a>
%e A071119 31513 is in the sequence because 31513, 151 and 5 are primes.
%e A071119 a(17) = 39293 because 39293, 929 and 2 are primes.
%o A071119 (PARI) V = [2, 3, 5, 7]; vCount = 4; x = [1, 3, 7, 9]; print(V); forstep 
               (i = 2, 20, 2, newV = vector(4*vCount); newCount = 0; for (j = 1, 
               4, for (k = 1, vCount, n = x[j]*(10^i + 1) + 10*V[k]; if (isprime(n), 
               print(n); newCount = newCount + 1; newV[newCount] = n))); V = newV; 
               vCount = newCount) - David Wasserman (wasserma(AT)spawar.navy.mil), 
               Oct 04 2004
%Y A071119 Cf. A002385.
%Y A071119 Sequence in context: A039944 A076611 A082805 this_sequence A157869 A046705 
               A054218
%Y A071119 Adjacent sequences: A071116 A071117 A071118 this_sequence A071120 A071121 
               A071122
%K A071119 base,easy,fini,full,nonn
%O A071119 1,1
%A A071119 Lior Manor (lior.manor(AT)gmail.com) May 28 2002
%E A071119 Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion 
               of Andrew Plewe, May 14 2007