

A231426


Least prime such that at most n digits may be appended to the right, preserving primality at each step.


1



53, 11, 97, 17, 71, 43, 13, 2, 19, 103, 409, 1457011
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OFFSET

0,1


LINKS

Table of n, a(n) for n=0..11.


FORMULA

a(n) is the least prime p=prime(k) such that A232128(p) (= A232127(k)) = n.
If a(n) = p, then a(n) = floor(A232129(p)/10^A232128(p)).


EXAMPLE

a(7) = 2 is the least prime which starts several sequences of 1+7 primes, e.g., (2, 23, 239, 2393, ..., 23399339) and others leading at most to 29399999 = A232129(2), where a digit is appended 7 times to yield a prime after each step, while it is not possible in any of the "branches" to append one more digit to the last term, preserving primality.


CROSSREFS

Cf. A232128, A232127, A232126, A232125.
Sequence in context: A143294 A143428 A143385 * A048602 A048606 A033373
Adjacent sequences: A231423 A231424 A231425 * A231427 A231428 A231429


KEYWORD

nonn,base,more


AUTHOR

Michel Marcus and M. F. Hasler, Nov 19 2013


STATUS

approved



