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%I #17 Oct 16 2023 12:03:53
%S 2,3,5,7,131,151,353,373,727,757,929,11311,31513,33533,37273,37573,
%T 39293,71317,93739,97579,1335331,3315133,3392933,7392937,9375739,
%U 373929373,733929337
%N 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 J.-P. Delahaye, "Pour la science", (French edition of Scientific American), Juin 2002, p. 99.
%D G. L. Honaker, Jr. and C. Caldwell, Palindromic prime pyramids, J. Recreational Mathematics, vol. 30.3, pp. 169-176, 1999-2000.
%H 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 G. L. Honaker, Jr. and C. K. Caldwell, <a href="http://www.utm.edu/staff/caldwell/supplements">Supplement to "Palindromic Prime Pyramids"</a>
%H I. Peterson, MathTrek, <a href="http://www.maa.org/mathland/mathtrek_08_29_05.html">Primes, Palindromes and Pyramids</a>
%e 31513 is in the sequence because 31513, 151 and 5 are primes.
%e a(17) = 39293 because 39293, 929 and 2 are primes.
%o (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_, Oct 04 2004
%Y Cf. A002385.
%K base,easy,fini,full,nonn
%O 1,1
%A _Lior Manor_, May 28 2002
%E Edited by _N. J. A. Sloane_ at the suggestion of _Andrew S. Plewe_, May 14 2007
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