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 A074365 Smallest prime > the concatenation of the first n natural numbers. 2
 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)
 OFFSET 1,1 LINKS Michael S. Branicky, Table of n, a(n) for n = 1..369 (all terms with <= 1000 digits). EXAMPLE The first prime > 123, the concatenation of the first three natural numbers, is 127. Hence a(3) = 127. MAPLE a:= n-> nextprime(parse(cat(\$1..n))): seq(a(n), n=1..19);  # Alois P. Heinz, Feb 13 2021 MATHEMATICA 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 *) PROG (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 CROSSREFS Sequence in context: A151361 A328008 A073559 * A071362 A108471 A036078 Adjacent sequences:  A074362 A074363 A074364 * A074366 A074367 A074368 KEYWORD base,nonn AUTHOR Joseph L. Pe, Sep 26 2002 EXTENSIONS More terms from Lior Manor Oct 08 2002 a(18) and beyond from Michael S. Branicky, Feb 13 2021 STATUS approved

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Last modified July 1 09:41 EDT 2022. Contains 354958 sequences. (Running on oeis4.)