[seqfan] a(n) divides concat(a(1) ... a(n))
David Scambler
dscambler at bmm.com
Thu Sep 30 08:37:56 CEST 2010
For this sequence start with a(1) = 1 then find a(n) = smallest number > a(n-1) such that a(n) divides concat(a(1), a(2), ..., a(n))
1: 1 divides 1
1,2: 2 divides 12
1,2,3: 3 divides 123
1,2,3,4: 4 does NOT divide 1234, so
1,2,3,5: 5 divides 1235
Etc.
S = 1 2 3 5 10 12 15 20 25 30 39 44 50 100 101 125 150 188 200 220 230 250 272 304 320 370 376 400 500 525 600 615 625 1000 1250 1487 ...
Primes appearing so far are 2,3,39,101,1487. I don't know whether more primes will appear. I have only checked up to a(110) = 120000.
Cheers
dave
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