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#20 by Giovanni Resta at Tue Oct 18 10:45:23 EDT 2022
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#19 by Michel Marcus at Tue Oct 18 10:29:28 EDT 2022
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#18 by Michael S. Branicky at Tue Oct 18 10:28:48 EDT 2022
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#17 by Michael S. Branicky at Tue Oct 18 10:28:45 EDT 2022
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| PROG
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(Python)
from sympy import isprime
from itertools import count
def a(n): return next(k for k in count(n+1) if isprime(int(str(n)+str(k))))
print([a(n) for n in range(1, 68)]) # Michael S. Branicky, Oct 18 2022
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| STATUS
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approved
editing
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#16 by N. J. A. Sloane at Fri Nov 13 23:10:22 EST 2020
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#15 by N. J. A. Sloane at Fri Nov 13 23:10:20 EST 2020
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| NAME
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a(n) is the smallest number m>n such that the concatenation nm is prime, or -1 if no such m exists.
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| COMMENTS
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IsMax Alekseyev (see therelink ain proofA068695) shows that a(n) always exists?. - _N. J. A. Sloane_, Nov 13 2020
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| EXTENSIONS
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Escape clause added to definition by N. J. A. Sloane, Nov 08 2020
Under construction - do not touch - N. J. A. Sloane, Nov 10 2020
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#14 by N. J. A. Sloane at Wed Nov 11 20:01:11 EST 2020
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| LINKS
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<a href="/index/Pri#piden">Index entries for primes involving decimal expansion of n</a>
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#13 by N. J. A. Sloane at Tue Nov 10 14:18:45 EST 2020
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| EXTENSIONS
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Under construction - do not touch - N. J. A. Sloane, Nov 10 2020
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| STATUS
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approved
editing
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#12 by N. J. A. Sloane at Sun Nov 08 01:31:56 EST 2020
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#11 by N. J. A. Sloane at Sun Nov 08 01:31:51 EST 2020
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| NAME
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a(n) is the smallest number m>n such that the concatenation nm is prime, or -1 if no such m exists.
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| EXTENSIONS
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Escape clause added to definition by N. J. A. Sloane, Nov 08 2020
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| STATUS
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approved
editing
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