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A246801 Primes of the form: concatenation n with n-th composite integer. 2
4057, 4463, 4969, 5881, 6691, 86117, 90121, 129169, 131171, 136177, 160207, 162209, 169217, 193247, 225287, 252319, 265333, 272341, 280351, 288361, 297371, 327407, 346429, 355441, 388481, 410507, 429529, 451553, 456559, 474581 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..10000

EXAMPLE

4057 is in the sequence since 40th composite integer is 57 and 4057 is prime.

MATHEMATICA

w = Select[Range[2, 800], ! PrimeQ[#] &]; Select[

Table[FromDigits[Flatten[{IntegerDigits[n], IntegerDigits[w[[n]]]}]], {n, 480}], PrimeQ]

PROG

(Python)

import sympy

from sympy import isprime

c = 0

for n in range(2, 10**5):

..if not isprime(n):

....c += 1

....p = str(c)+str(n)

....if isprime(p):

......print(int(p), end=', ')

# Derek Orr, Sep 18 2014

CROSSREFS

Cf. A000040, A002808, A191992.

Sequence in context: A108006 A320207 A320216 * A020430 A163010 A069332

Adjacent sequences:  A246798 A246799 A246800 * A246802 A246803 A246804

KEYWORD

nonn,base

AUTHOR

Jahangeer Kholdi, Sep 15 2014

STATUS

approved

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Last modified May 17 05:13 EDT 2021. Contains 343965 sequences. (Running on oeis4.)