The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A113604 Define f(k) = k + sum of digits of n. a(n) is the first prime that results by applying f zero or more times to n, or 0 if no such prime exists. 0

%I #5 Dec 05 2013 19:57:07

%S 2,2,3,23,5,0,7,23,0,11,11,0,13,19,0,23,17,0,19,41,0,41,23,0,37,41,0,

%T 101,29,0,31,37,0,41,43,0,37,101,0,59,41,0,43,59,0,67,47,0,101,89,0,

%U 59,53,0,89,67,0,71,59,0,61,101,0,127,89,0,67,103,0,101,71,0,73,127,0,89

%N Define f(k) = k + sum of digits of n. a(n) is the first prime that results by applying f zero or more times to n, or 0 if no such prime exists.

%C a(n) = n for n prime; a(n) = 0 for n > 3 and n == 0 (mod 3).

%C Conjecture: a(n) = 0 only if n == 0 (mod 3).

%e a(4) = 23 since f(4) = 4+4 = 8, f(8) = 8+8 = 16, f(16) = 16+1+6 = 23.

%o (PARI) f(n) = local(k,s,d);k=n;s=0;while(k>0,d=divrem(k,10);k=d[1];s=s+d[2]);s+n {m=76;for(n=1,m,if(n>3&&n%3==0,print1(0,","),k=n;z=1000*n;while(k<z&&!isprime(k),k=f(k));print1(if(k<z,k,0),",")))}

%Y Cf. A113605.

%K base,easy,nonn

%O 1,1

%A _Amarnath Murthy_, Nov 09 2005

%E Edited and extended by _Klaus Brockhaus_, Nov 10 2005

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 May 28 12:20 EDT 2024. Contains 372913 sequences. (Running on oeis4.)