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A133757 Total number of restricted right truncatable primes in base n.

%I A133757 #15 Feb 16 2025 08:33:06
%S A133757 0,1,2,4,11,7,20,23,27,28,61,61,153,130,151,157,301,343,561,806,1046,
%T A133757 615,1227,2136,2472,2288,3685,2110,5241,4798,7017,10630,14175,14127,
%U A133757 21267,15034,24677,29289,46814,29291,63872,58451,82839,143678,196033,99103,218108
%N A133757 Total number of restricted right truncatable primes in base n.
%C A133757 Prime digits p in base n are counted if there is no prime with 2 digits which can have its rightmost digit removed to produce p.
%H A133757 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 A133757 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TruncatablePrime.html">Truncatable Prime</a>.
%H A133757 <a href="/index/Tri#tprime">Index entries for sequences related to truncatable primes</a>
%o A133757 (Python)
%o A133757 from sympy import isprime, primerange
%o A133757 def fromdigits(digs, base):
%o A133757     return sum(d*base**i for i, d in enumerate(digs))
%o A133757 def a(n):
%o A133757     prime_lists, an = [(p, ) for p in primerange(1, n)], 0
%o A133757     digits = 1
%o A133757     while len(prime_lists) > 0:
%o A133757         new_prime_strs = set()
%o A133757         for p in prime_lists:
%o A133757             can_extend = False
%o A133757             for d in range(n):
%o A133757                 c = (d, ) + p
%o A133757                 if isprime(fromdigits(c, n)):
%o A133757                     can_extend = True
%o A133757                     new_prime_strs.add(c)
%o A133757             if not can_extend:
%o A133757                 an += 1
%o A133757         prime_lists = list(new_prime_strs)
%o A133757         digits += 1
%o A133757     return an
%o A133757 print([a(n) for n in range(2, 27)]) # _Michael S. Branicky_, Dec 11 2022
%Y A133757 Cf. A076586.
%K A133757 nonn
%O A133757 2,3
%A A133757 _Martin Renner_, Jan 04 2008
%E A133757 a(6) corrected and a(11) and beyond from _Michael S. Branicky_, Dec 11 2022