Ambiguity in sequence A073175 First occurrence of an n-digit prime as a substring in the concatenation of the natural numbers
Jonathan Post
jvospost3 at gmail.com
Fri Aug 22 22:27:21 CEST 2008
A073175 First occurrence of an n-digit prime as a substring in the
concatenation of the natural numbers
12345678910111213141516171819202122232425262728293031....
Is there not a problem when the "n-digit" prime found by a greedy
algorithm is a substring starting with a zero not proper for OEIS
format, or does the definition gave to be amended to eliminate this?
By the way, the semiprime analogue would seem to be:
First occurrence of an n-digit semiprime as a substring in the
concatenation of the natural numbers
12345678910111213141516171819202122232425262728293031....
n a(n) comment
1 4 A001358(1)
2 34 semiprime(12)
3 123 semiprime(42)
4 1234 semiprime(363)
5 34567 semiprime(8514)
6 891011 = 11 * 81001
7 1234567 = 127 * 9721
8 10111213 = 7 * 1444459
9 910111213 = 11 * 82737383
10 3456789101 = 359 * 9628939
11 23456789101 = 37 * 633967273
12 123456789101 = 9091 * 13580111
13 6789101112131 = 13 * 522238547087
14 13141516171819 = 7 * 1877359453117
15 234567891011121 = 3 * 78189297003707
16 3456789101112131 = 1117 * 3094708237343
17 23456789101112131 = 14293 * 1641138256567
18 223242526272829303 = 2633 * 84786375340991
19 4567891011121314151 = 11 * 415262819192846741
20 34567891011121314151 = 449 * 76988621405615399
is that right?
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