

A089762


a(1) = 1, then nonzero digits ( 1 to 9) such that every nth concatenation is prime if n is prime else it is composite. The previous digits are so chosen that a single digit with prime index gives a prime.


0



1, 1, 3, 1, 1, 2, 1, 1, 1, 2, 9, 1, 1, 1, 1, 4, 3, 4, 3, 1, 1, 1, 3, 1, 1, 1, 1, 4, 1, 2, 3, 1, 1, 1, 2, 5, 9, 1, 1, 6, 9, 9, 1, 1, 2, 2, 7, 1, 1, 1, 2, 3, 9, 1, 1, 1, 1, 7, 1, 7, 9, 1, 1, 1, 7, 5, 3, 1, 2, 8, 3, 3, 7, 1, 1, 1, 3, 4, 7, 1, 1, 5, 9, 1, 1, 1, 1, 7, 3, 1, 1, 1, 1, 1, 1, 4, 9, 1, 1, 5, 7, 9, 3, 4, 3
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OFFSET

1,3


COMMENTS

This is the lexicographically least sequence that fits the rule through 114 digits. There is no guarantee that it can be extended indefinitely.  David Wasserman, Oct 06 2005


LINKS

Table of n, a(n) for n=1..105.


EXAMPLE

The first 11 partial concatenations are 1,11,113,1131,11311,113112,1131121,11311211,113112111,1131121112,11311211129.
The 2nd, 3rd, 5th 7th and 11th terms are primes. rest are composite.


PROG

(PARI) num = 111; n = 3; while (n < 115, isp = isprime(n); while (num%10 && isprime(num) != isp, num++); if (num%10, n++; num = 10*num + 1, num = (num  1)\10 + 1; n)); num\10; (David Wasserman, Sep 20 2005)


CROSSREFS

Sequence in context: A285770 A174820 A099501 * A257567 A318440 A307790
Adjacent sequences: A089759 A089760 A089761 * A089763 A089764 A089765


KEYWORD

nonn,base


AUTHOR

Amarnath Murthy, Nov 22 2003


EXTENSIONS

More terms from David Wasserman, Oct 06 2005
Edited by Charles R Greathouse IV, Apr 29 2010


STATUS

approved



