A094335 Largest right-truncatable prime number in base n if 1 is considered as a prime (written in base 10).

47, 71, 2039, 2437, 108863, 33487, 4497359, 1355840309, 1979339339, 6774006887, 2081628860747539, 122311273757, 6525460043032393259, 927920056668659, 1429175974256442233, 4928397730238375565449, 5228233855704101657

Offset

2,1

Links

Max Alekseyev, Table of n, a(n) for n = 2..75

I. O. Angell, and H. J. Godwin, On Truncatable Primes, Math. Comput. 31, 265-267, 1977.

Domingo Gómez-Pérez, Alina Ostafe, Min Sha, The Arithmetic of Consecutive Polynomial Sequences over Finite Fields, arXiv:1509.01936 [math.NT], 2015.

A. J. van der Poorten, A quote, Math. Intelligencer 7(2) (1985), 40.

Index entries for sequences related to truncatable primes

Example

Example for n=10: 1,19,197,1979,19793,197933,1979339,19793393,197933933 and 1979339339 are all prime numbers.

Prog

(PARI) a(n) = my(S, m, D); D=select(x->(gcd(x, n)==1), vector(n-1, j, j)); S=concat([1], select(ispseudoprime, vector(n, j, j))); while(#S, m=vecmax(S); S=concat(vector(#D, j, select(ispseudoprime, vector(#S, i, S[i]*n+D[j])))); ); m /* Max Alekseyev, Dec 06 2014 */

Crossrefs

Cf. A023107 (where 1 is not considered to be prime).

Sequence in context: A033231 A139923 A097458 * A300165 A316351 A282633

Adjacent sequences: A094332 A094333 A094334 * A094336 A094337 A094338

Keyword

base,nonn

Author

Martin Raab, Jun 04 2004

Status

approved