A076586 Total number of right truncatable primes in base n.
0, 4, 7, 14, 36, 19, 68, 68, 83, 89, 179, 176, 439, 373, 414, 473, 839, 1010, 1577, 2271, 2848, 1762, 3376, 5913, 6795, 6352, 10319, 5866, 14639, 13303, 19439, 29982, 38956, 39323, 58857, 41646, 68371, 80754, 128859, 81453, 175734, 161438, 228543, 396274, 538797
Offset: 2
Links
- Seth A. Troisi, Table of n, a(n) for n = 2..100 (terms n=2..53 from Martin Renner)
- I. O. Angell and H. J. Godwin, On Truncatable Primes, Math. Comput. 31, 265-267, 1977.
- Index entries for sequences related to truncatable primes
Programs
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Python
from sympy import isprime, primerange from sympy.ntheory.digits import digits def fromdigits(digs, base): return sum(d*base**i for i, d in enumerate(digs)) def a(n): prime_lists, an = [(p,) for p in primerange(1, n)], 0 digits = 1 while len(prime_lists) > 0: an += len(prime_lists) candidates = set((d,)+p for p in prime_lists for d in range(1, n)) prime_lists = [c for c in candidates if isprime(fromdigits(c, n))] digits += 1 return an print([a(n) for n in range(2, 27)]) # Michael S. Branicky, May 03 2022
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