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A152397 Similar to A152396, but here the requirement is for finding any n primes, not necessarily from the shortest concatenations. 2
4, 10, 73, 100, 8338 (list; graph; refs; listen; history; text; internal format)



Tentatively, as of Dec 2012, the likely value of a(6) is 20968. A noteworthy fact, perhaps, is that were this sequence to limit itself to non-titanic primes (ones under 10^999), then it would look the same to the point shown and have the stated tentative value for a(6) as its a(5), despite there being a number of smaller values eventually reaching a 5th prime. - James G. Merickel, Dec 06 2012

a(5)=8338 has not been determined with complete certainty, but is likely correct (See A232657). a(6)=20968 has fairly convincing support, but even finding a good upper bound for a(7) is hard. - James G. Merickel, Jun 14 2014


Table of n, a(n) for n=1..5.


21, 32, and 321 are all composite, and 43 is prime. So a(1)=4. Then the first stem resulting in 2 primes is 10, with 109 and 10987 both prime. So a(2)=10. 73 produces 4 primes in this way if improper concatenation (including 73 itself) is included, but it is not. Since stem values from 11 through 72 never produce more than 2 primes properly, a(3)=73.


Cf. A152396, A232657.

Sequence in context: A207160 A244297 A207159 * A239502 A171754 A215872

Adjacent sequences:  A152394 A152395 A152396 * A152398 A152399 A152400




James G. Merickel, Oct 20 2009


a(5) added by James G. Merickel, Feb 06 2014



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Last modified February 26 11:15 EST 2021. Contains 341631 sequences. (Running on oeis4.)