This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A071119 #17 Oct 16 2023 12:03:53 %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_, Oct 04 2004 %Y A071119 Cf. A002385. %K A071119 base,easy,fini,full,nonn %O A071119 1,1 %A A071119 _Lior Manor_, May 28 2002 %E A071119 Edited by _N. J. A. Sloane_ at the suggestion of _Andrew S. Plewe_, May 14 2007