20100401, 03:33  #1 
Aug 2004
New Zealand
13·17 Posts 
Smarandache semiprimes
Sequence A046461 Sloane's OEIS, about finding semiprime Smarandache numbers (concatenation the positive integers, Sm(11)=1234567891011, etc.). The known values this sequence are 3, 4, 7, 34, 97. For example, Sm(34) = 2 * 6172839455055606570758085909601061116212631364146515661667.
Further searching indicates the only other possible members below 2300, are: Code:
Sm(631) Sm(691) Sm(859) Sm(1033) Sm(1051) Sm(1291) Sm(1651) Sm(1657) Sm(1831) Sm(1951) Sm(2041) Sm(2047) Sm(2107) I've run 100 ecm curves with b1=10000 each candidate, but nothing with higher limits. 
20100401, 03:36  #2 
Aug 2004
New Zealand
13·17 Posts 
Hmm, for some reason the forum i.s losing two letter words like i.s from m.y posts.

20100401, 13:59  #3 
"Ed Hall"
Dec 2009
Adirondack Mtns
3546_{10} Posts 

20100401, 14:21  #4 
Aug 2006
2·11·271 Posts 
Ugh, ,base,sequences. I'll take Sm(631) t.o 250,000.

20100401, 16:59  #6 
Feb 2006
Denmark
346_{8} Posts 
PrimeForm/GW has found Sm(5053) = 133283 * prp19099.
I'm not attempting to prove the prp. 
20100401, 17:50  #7 
Aug 2006
2·11·271 Posts 

20100402, 12:38  #8 
Feb 2006
Denmark
2·5·23 Posts 
Sm(9706) = 2 * prp37716, found by PrimeForm/GW.

20100402, 12:39  #9 
Aug 2006
2·11·271 Posts 
Sm(631) = 414941628631826493984534937401473 * C1752
Working on Sm(691) now. Last fiddled with by CRGreathouse on 20100402 at 13:15 
20100405, 19:58  #10 
Aug 2004
New Zealand
13×17 Posts 
Many thanks for the Sm(631) and the results for higher n. In a few days I will submit some extra comments on the OEIS entry.

20100405, 21:47  #11 
Aug 2006
2×11×271 Posts 

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