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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.
2
2, 3, 5, 7, 131, 151, 353, 373, 727, 757, 929, 11311, 31513, 33533, 37273, 37573, 39293, 71317, 93739, 97579, 1335331, 3315133, 3392933, 7392937, 9375739, 373929373, 733929337
OFFSET
1,1
REFERENCES
J.-P. Delahaye, "Pour la science", (French edition of Scientific American), Juin 2002, p. 99.
G. L. Honaker, Jr. and C. Caldwell, Palindromic prime pyramids, J. Recreational Mathematics, vol. 30.3, pp. 169-176, 1999-2000.
LINKS
G. L. Honaker, Jr. and C. K. Caldwell, Palindromic Prime Pyramids
G. L. Honaker, Jr. and C. K. Caldwell, Supplement to "Palindromic Prime Pyramids"
I. Peterson, MathTrek, Primes, Palindromes and Pyramids
EXAMPLE
31513 is in the sequence because 31513, 151 and 5 are primes.
a(17) = 39293 because 39293, 929 and 2 are primes.
PROG
(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
CROSSREFS
Cf. A002385.
Sequence in context: A039944 A076611 A082805 * A157869 A046705 A054218
KEYWORD
base,easy,fini,full,nonn
AUTHOR
Lior Manor, May 28 2002
EXTENSIONS
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, May 14 2007
STATUS
approved