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

%I A023107 #42 Feb 16 2025 08:32:34
%S A023107 71,191,2437,108863,6841,4497359,1355840309,73939133,6774006887,
%T A023107 18704078369,122311273757,6525460043032393259,927920056668659,
%U A023107 16778492037124607,4928397730238375565449,5228233855704101657,3013357583408354653,1437849529085279949589,101721177350595997080671,185720479816277907890970001
%N A023107 Largest integer in which every prefix is prime in base n (written in base 10).
%C A023107 Or, largest right-truncatable prime with base n>2 (in decimal form).
%C A023107 a(n) <= A094335(n).
%H A023107 Martin Renner, Max Alekseyev and Giovanni Resta, <a href="/A023107/b023107.txt">Table of n, a(n) for n = 3..100</a>
%H A023107 I. O. Angell and H. J. Godwin, <a href="http://dx.doi.org/10.1090/S0025-5718-1977-0427213-2">On Truncatable Primes</a>, Math. Comput. 31, 265-267, 1977.
%H A023107 N. J. A. Sloane, <a href="/A023107/a023107.txt">The Angell-Godwin table of initial terms of A023107 and A103443</a>
%H A023107 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TruncatablePrime.html">Truncatable Prime</a>.
%H A023107 <a href="/index/Tri#tprime">Index entries for sequences related to truncatable primes</a>
%e A023107 a(100) = 70123916363515199416199518301698321195339012727994799// 190371992151279729974757397909992327936943877127375781091143. - _Giovanni Resta_, Apr 11 2016
%o A023107 (PARI) 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 */
%Y A023107 Cf. A076586.
%K A023107 nonn,base
%O A023107 3,1
%A A023107 _David W. Wilson_
%E A023107 More terms from _Don Reble_, Jun 23 2004
%E A023107 a(54)-a(75) in b-file from _Max Alekseyev_, Dec 09 2014
%E A023107 a(76)-a(100) in b-file from _Giovanni Resta_, May 01 2016