The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A236672 Start with 9; thereafter, primes obtained by concatenating to the end of previous term the next smallest number that will produce a prime. 1
 9, 97, 971, 9719, 971917, 97191713, 9719171333, 971917133323, 9719171333237, 971917133323777, 97191713332377731, 9719171333237773159, 971917133323777315951, 97191713332377731595127, 971917133323777315951277, 971917133323777315951277269 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n+1) is the next smallest prime beginning with a(n). Initial term is 9. After a(1), these are the primes in A069611. LINKS Robert Israel, Table of n, a(n) for n = 1..316 EXAMPLE a(1) = 9 by definition. a(2) is the next smallest prime beginning with 9, so a(2) = 97. a(3) is the next smallest prime beginning with 97, so a(3) = 971. MAPLE R:= 9: x:= 9: for i from 2 to 20 do for y from 1 by 2 do z:= x*10^(1+ilog10(y)) + y; if isprime(z) then R:= R, z; x:= z; break fi od od: R; # Robert Israel, Nov 22 2023 MATHEMATICA next[p_]:=Module[{i=1, q}, While[!PrimeQ[q=10^IntegerLength[i]p+i], i+=2]; q]; NestList[next, 9, 15] (* Paolo Xausa, Nov 23 2023 *) PROG (Python) import sympy from sympy import isprime def b(x): num = str(x) n = 1 while n < 10**3: new_num = str(x) + str(n) if isprime(int(new_num)): print(int(new_num)) x = new_num n = 1 else: n += 1 b(9) CROSSREFS Cf. A048553, A110773, A069611. Sequence in context: A284668 A232229 A240780 * A155699 A230620 A155601 Adjacent sequences: A236669 A236670 A236671 * A236673 A236674 A236675 KEYWORD nonn,base AUTHOR Derek Orr, Jan 29 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified August 5 23:35 EDT 2024. Contains 374957 sequences. (Running on oeis4.)