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A165449
Write the prime numbers in a string: 2357111317192329... (cf. A033308). The sequence gives the first position in the string for natural numbers.
3
5, 1, 2, 21, 3, 31, 4, 41, 12, 47, 5, 62, 7, 22, 77, 32, 9, 95, 11, 589, 110, 113, 1, 128, 131, 137, 63, 149, 15, 158, 8, 14, 123, 24, 2, 188, 19, 42, 72, 206, 21, 215, 23, 227, 233, 236, 25, 248, 75, 257, 78, 263, 27, 269, 275, 278, 3, 290, 29, 299, 31, 829
OFFSET
1,1
COMMENTS
Same as A229190 but omitting the a(0) term.
Defined for all a by the normality of the Copeland-Erdős constant. - Aaron Weiner, Sep 19 2013
LINKS
EXAMPLE
The first occurrence of "111" in the string is 5, so a(111)=5.
MAPLE
with(StringTools): s:="": for n from 1 to 300 do s:=cat(s, convert(ithprime(n), string)): od: seq(Search(convert(n, string), s), n=1..62); # Nathaniel Johnston, May 26 2011
MATHEMATICA
With[{prd=Flatten[IntegerDigits/@Prime[Range[1000]]], nn=10}, Flatten[ Table[ SequencePosition[ prd, IntegerDigits[ n], 1], {n, 70}], 1]][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 12 2019 *)
PROG
(Python)
from sympy import primerange
from itertools import count, takewhile
def afind(plimit):
s = "".join(str(p) for p in primerange(1, plimit+1))
return [1+s.find(str(n)) for n in takewhile(lambda i: str(i) in s, count(1))]
print(afind(10**4)) # Michael S. Branicky, May 01 2021
CROSSREFS
Cf. A229190 (same sequence but including the a(0) term).
Cf. A031297.
Sequence in context: A318430 A318098 A318068 * A019114 A201526 A091384
KEYWORD
easy,base,nonn
AUTHOR
Rémy Sigrist, Sep 20 2009
STATUS
approved