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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A243411 Least prime p such that p*10^n-1, p*10^n-3, p*10^n-7 and p*10^n-9 are all prime. 0
 2, 2, 10193, 24851, 20549, 719, 22133, 230471, 46679, 432449, 114689, 227603, 305297, 61463, 1866467, 866309, 1189403, 362081, 2615783, 493433, 966353, 4154363, 6562931, 9096203, 3701627, 3128813, 20983727, 303593, 24437537, 1068491 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..30. MATHEMATICA lpp[n_]:=Module[{p=2, c=10^n}, While[!AllTrue[p*c-{1, 3, 7, 9}, PrimeQ], p= NextPrime[ p]]; p]; Array[lpp, 30] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jun 12 2016 *) PROG (Python) import sympy from sympy import isprime from sympy import prime def a(n): ..for k in range(1, 10**8): ....if isprime(prime(k)*10**n-1) and isprime(prime(k)*10**n-3) and isprime(prime(k)*10**n-7) and isprime(prime(k)*10**n-9): ......return prime(k) n = 1 while n < 100: ..print(a(n), end=', ') ..n+=1 (PARI) a(n)=for(k=1, 10^8, if(ispseudoprime(prime(k)*10^n-1) && ispseudoprime(prime(k)*10^n-3) && ispseudoprime(prime(k)*10^n-7) && ispseudoprime(prime(k)*10^n-9), return(prime(k)))) n=1; while(n<100, print1(a(n), ", "); n++) CROSSREFS Cf. A242564, A064432. Sequence in context: A260753 A079237 A262060 * A013510 A013504 A230807 Adjacent sequences: A243408 A243409 A243410 * A243412 A243413 A243414 KEYWORD nonn AUTHOR Derek Orr, Jun 04 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 June 25 10:28 EDT 2024. Contains 373701 sequences. (Running on oeis4.)