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A074365
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Smallest prime > the concatenation of the first n natural numbers.
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2
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2, 13, 127, 1237, 12347, 123457, 1234577, 12345701, 123456791, 12345678923, 1234567891013, 123456789101119, 12345678910111223, 1234567891011121343, 123456789101112131449, 12345678910111213141523, 1234567891011121314151753, 123456789101112131415161869
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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Michael S. Branicky, Table of n, a(n) for n = 1..369 (all terms with <= 1000 digits).
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EXAMPLE
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The first prime > 123, the concatenation of the first three natural numbers, is 127. Hence a(3) = 127.
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MAPLE
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a:= n-> nextprime(parse(cat($1..n))):
seq(a(n), n=1..19); # Alois P. Heinz, Feb 13 2021
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MATHEMATICA
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p[n_] := Module[{r, i}, r = 2; i = 1; While[r <= n, i = i + 1; r = Prime[i]]; r]; s = ""; a = {}; Do[s = s <> ToString[Prime[i]]; a = Append[a, p[ToExpression[s]]], {i, 1, 8}]; a
Table[NextPrime[FromDigits[Flatten[IntegerDigits/@Range[n]]]], {n, 20}] (* Harvey P. Dale, Jan 16 2018 *)
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PROG
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(Python)
from sympy import nextprime
def a(n):
return nextprime(int("".join(map(str, (i for i in range(1, n+1)))))-1)
print([a(n) for n in range(1, 19)]) # Michael S. Branicky, Feb 13 2021
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CROSSREFS
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Sequence in context: A151361 A328008 A073559 * A071362 A108471 A036078
Adjacent sequences: A074362 A074363 A074364 * A074366 A074367 A074368
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KEYWORD
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base,nonn
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AUTHOR
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Joseph L. Pe, Sep 26 2002
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EXTENSIONS
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More terms from Lior Manor Oct 08 2002
a(18) and beyond from Michael S. Branicky, Feb 13 2021
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STATUS
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approved
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