[seqfan] 9-digit accepting integers
Eric Angelini
Eric.Angelini at kntv.be
Mon Oct 27 12:53:19 CET 2014
Hello SeqFans,
21123 has the property that every pair of adjacent digits sum to a prime number
(thus belonging to https://oeis.org/A182175).
We want to transform this integer into another integer having the same property
by inserting single digits somewhere:
21123 + 0 = 211230
21123 + 1 = 121123
21123 + 2 = 211232
21123 + 3 = 321123
21123 + 4 = 211234
21123 + 5 = 521123
21123 + 6 = 216123
21123 + 7 = impossible
21123 + 8 = 211238
21123 + 9 = 921123
I think no integer will ever accept the 10 digits from 0 to 9.
Is 21123 the smallest accepting 9 digits? What are the others
(like 41123, accepting 7 now, but not 5)?
Best,
É.
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