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Search: id:A049462
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| A049462 |
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a(n) = smallest n-digit prime p such that the concatenation a(1)a(2)...a(n-1)p is prime, with a(1) = 2. |
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+0
1
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| 2, 11, 151, 1013, 10867, 100673, 1000357, 10000931, 100000213, 1000000901, 10000001797, 100000000283, 1000000001911, 10000000012553, 100000000006087, 1000000000011317, 10000000000003471, 100000000000017431
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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Starting with an initial prime of 2, next the smallest 2-digit prime which gives a prime is 11 (211, a prime), then 151 (3-digit prime) is smallest to make 211151 a prime, etc.
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MATHEMATICA
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NextPrim[n_] := Block[{k = n + 1}, While[ ! PrimeQ[k], k++ ]; k]; a[1] = 2; a[n_] := a[n] = Block[{p = Sum[ a[i]*10^(n(n + 1)/2 - i(i + 1)/2), {i, 1, n - 1}], q = NextPrim[10^(n - 1)]}, While[ !PrimeQ[p + q], q = NextPrim[q]]; q]; Table[ a[n], {n, 1, 19}] (from Robert G. Wilson v)
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CROSSREFS
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Sequence in context: A046912 A006122 A111014 this_sequence A058154 A067968 A013050
Adjacent sequences: A049459 A049460 A049461 this_sequence A049463 A049464 A049465
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KEYWORD
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nonn,base
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AUTHOR
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Jeff Heleen (meriaden(AT)hotmail.com), Oct 13 2003
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 18 2003
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