

A089829


Triangle T(p,k) read by rows, where p runs through the odd primes and 2 <= k <= p1. T(p,k) = 1 if the reverse of the basek expansion of p is a prime, otherwise 0.


1



1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 0
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OFFSET

3,1


COMMENTS

Row p has p2 terms.
A very large version of this pyramid, with 1's replaced with white dots and 0's replaced with black dots, shows a very interesting pattern (see link). The author says: "These primes form a pattern similar to an astronomical radiant (the point in the sky from which a meteor shower appears to originate)".


LINKS

Table of n, a(n) for n=3..107.
C. E. Nichols, Radiant Prime, 2003


EXAMPLE

Writing 11 in bases 2 through 10, we obtain
1011,102,23,21,15,14,13,12,11. Reversing these, we obtain
1101,201,32,12,51,41,31,21,11. Now 32 (base 4) and 31 (octal) are composite, all others are prime, so the row for 11 reads.
1,1,0,1,1,1,0,1,1
Triangle begins:
.1
.1 1 1
.1 1 1 1 1
.1 1 0 1 1 1 0 1 1
....


CROSSREFS

See A074481 for another version.
Sequence in context: A014295 A103447 A123927 * A178788 A131217 A105567
Adjacent sequences: A089826 A089827 A089828 * A089830 A089831 A089832


KEYWORD

base,easy,nonn,tabf


AUTHOR

Sam Alexander, Nov 12 2003


STATUS

approved



