A037047 Starting at n, "say what you see"; sequence gives number of primes obtained before first composite number appears.

1, 0, 1, 0, 0, 0, 2, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0

Offset: 1

Author

G. L. Honaker, Jr.

Keywords

• nonn
• base

Comments

If n itself is a prime, it is not included in the count. - Antti Karttunen, Feb 13 2019

Examples

			1 -> 11 (prime) -> 21 (composite), so a(1) = 1.
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• P. De Geest, World!Of Palindromic Primes

Crossrefs

Cf. A005150, A036978, A045918.

Programs

PARI

A045918(a) = { my(c=1); for(j=2, #a=Vec(Str(a)), if(a[j-1]==a[j], a[j-1]=""; c++, a[j-1]=Str(c, a[j-1]); c=1)); a[#a]=Str(c, a[#a]); eval(concat(a)) }; \\ From A045918 by M. F. Hasler, Jan 27 2012
A037047(n) = if(1==n,n,my(c=0); while(1, n = A045918(n); if(isprime(n), c++, return(c)))); \\ Antti Karttunen, Feb 13 2019

Extensions

More terms from Antti Karttunen, Feb 13 2019