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A089829 Triangle T(p,k) read by rows, where p runs through the odd primes and 2 <= k <= p-1. T(p,k) = 1 if the reverse of the base-k 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

Row p has p-2 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

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Last modified September 20 12:42 EDT 2018. Contains 315239 sequences. (Running on oeis4.)