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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A217046 Primes that remain prime when a single "6" digit is inserted between any two adjacent decimal digits. 4
 13, 17, 23, 29, 37, 41, 43, 47, 53, 59, 61, 71, 79, 83, 97, 101, 109, 113, 137, 157, 163, 167, 263, 277, 293, 307, 313, 317, 331, 397, 421, 443, 457, 463, 569, 607, 653, 659, 661, 673, 691, 739, 769, 787, 809, 823, 829, 863, 881, 977, 997, 1063, 1087, 1453 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Paolo P. Lava & Harvey P. Dale, Table of n, a(n) for n = 1..500 (First 262 terms from Paolo P. Lava) EXAMPLE 185917 is prime and also 1859167, 1859617, 1856917, 1865917 and 1685917. MAPLE with(numtheory); A217044:=proc(q, x) local a, b, c, i, n, ok; for n from 5 to q do a:=ithprime(n); b:=0; while a>0 do b:=b+1; a:=trunc(a/10); od; a:=ithprime(n); ok:=1; for i from 1 to b-1 do c:=a+9*10^i*trunc(a/10^i)+10^i*x; if not isprime(c) then ok:=0; break; fi; od; if ok=1 then print(ithprime(n)); fi; od; end: A217044(100000, 6) MATHEMATICA Select[Prime[Range[5, 1200]], And@@PrimeQ[FromDigits/@Table[ Insert[ IntegerDigits[ #], 6, i], {i, 2, IntegerLength[#]}]]&] (* Harvey P. Dale, Oct 09 2012 *) PROG (PARI) is(n)=my(v=concat([""], digits(n))); for(i=2, #v-1, v[1]=Str(v[1], v[i]); v[i]=6; if(i>2, v[i-1]=""); if(!isprime(eval(concat(v))), return(0))); isprime(n) \\ Charles R Greathouse IV, Sep 26 2012 CROSSREFS Cf. A050674, A050711-A050719, A069246, A159236, A215417, A215419-A215421, A217044, A217045, A217047, A217062-A217065 Sequence in context: A316603 A235914 A050716 * A141076 A092146 A207991 Adjacent sequences: A217043 A217044 A217045 * A217047 A217048 A217049 KEYWORD nonn,base AUTHOR Paolo P. Lava, Sep 25 2012 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 6 15:20 EDT 2023. Contains 363148 sequences. (Running on oeis4.)