A094335 -id:A094335 - cp's OEIS frontend

A023107 Largest integer in which every prefix is prime in base n (written in base 10).

71, 191, 2437, 108863, 6841, 4497359, 1355840309, 73939133, 6774006887, 18704078369, 122311273757, 6525460043032393259, 927920056668659, 16778492037124607, 4928397730238375565449, 5228233855704101657, 3013357583408354653, 1437849529085279949589, 101721177350595997080671, 185720479816277907890970001

Offset: 3

David W. Wilson

Or, largest right-truncatable prime with base n>2 (in decimal form).

a(n) <= A094335(n).

			a(100) = 70123916363515199416199518301698321195339012727994799// 190371992151279729974757397909992327936943877127375781091143. - _Giovanni Resta_, Apr 11 2016

Martin Renner, Max Alekseyev and Giovanni Resta, Table of n, a(n) for n = 3..100
I. O. Angell and H. J. Godwin, On Truncatable Primes, Math. Comput. 31, 265-267, 1977.
N. J. A. Sloane, The Angell-Godwin table of initial terms of A023107 and A103443
Eric Weisstein's World of Mathematics, Truncatable Prime.
Index entries for sequences related to truncatable primes

Cf. A076586.

a(n) = my(S,m,D); D=select(x->(gcd(x,n)==1),vector(n-1,j,j)); S=select(ispseudoprime,vector(n-1,i,i)); while(#S, m=vecmax(S); S=concat(vector(#D,j,select(ispseudoprime,vector(#S,i,S[i]*n+D[j]))));); m /* Max Alekseyev, Dec 09 2014 */

More terms from Don Reble, Jun 23 2004
a(54)-a(75) in b-file from Max Alekseyev, Dec 09 2014
a(76)-a(100) in b-file from Giovanni Resta, May 01 2016

A012883 Numbers in which every prefix (in base 10) is 1 or a prime.

Original entry on oeis.org

1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 53, 59, 71, 73, 79, 113, 131, 137, 139, 173, 179, 191, 193, 197, 199, 233, 239, 293, 311, 313, 317, 373, 379, 593, 599, 719, 733, 739, 797, 1319, 1373, 1399, 1733, 1913, 1931, 1933, 1973, 1979, 1993, 1997, 1999

Offset: 1

Larry Calmer (larry(AT)wri.com), Simon Plouffe

T. D. Noe, Table of n, a(n) for n=1..147 (complete sequence)

Cf. A024770 (every prefix is prime).

max = 10^10; truncate[p_] := If[q = Quotient[p, 10]; q == 1 || PrimeQ[q], q, p]; ok[p_] := FixedPoint[truncate, p] < 10; p = 1; cnt = 2; A012883 = Join[{1}, Reap[While[(p = NextPrime[p]) < max, If[ok[p], Print[cnt++, " ", p]; Sow[p]]]][[2, 1]]] (* Jean-François Alcover, Nov 23 2015 *)

for(n=1, 1e4, k=n; while(isprime(n) || n==1, c=n; n=(c-lift(Mod(c, 10)))/10); if(n==0, print1(k, ", ")); n=k) \\ Altug Alkan, Nov 23 2015

Last term is A094335(10) = 1979339339 (confirmed by David W. Wilson ).

cp's OEIS Frontend

A023107 Largest integer in which every prefix is prime in base n (written in base 10).

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