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 A074481 Triangle T(p,k) read by rows, where p runs through the primes and 1 <= 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, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 0, 1, 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, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS Row p has p-1 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 C. E. Nichols, Radiant Prime, 2003 EXAMPLE Writing 11 in bases 1 through 10, we obtain 11111111111,1011,102,23,21,15,14,13,12,11. Reversing these, we obtain 11111111111,1101,201,32,12,51,41,31,21,11. Now 32 (base 4) and 31 (octal) are composite, all others are prime, so the row for 11 reads. 1,1,1,0,1,1,1,0,1,1 Triangle begins: .1 .1 1 .1 1 1 1 .1 1 1 1 1 1 .1 1 1 0 1 1 1 0 1 1 .... CROSSREFS See A089829 for another version. Sequence in context: A167851 A053865 A166234 * A015420 A015522 A015658 Adjacent sequences:  A074478 A074479 A074480 * A074482 A074483 A074484 KEYWORD base,easy,nonn,tabf AUTHOR C. E. Nichols (radprime(AT)radiantprimes.com), Nov 19 2003 EXTENSIONS More terms from Ray Chandler, Nov 22 2003 STATUS approved

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Last modified August 20 00:52 EDT 2018. Contains 313902 sequences. (Running on oeis4.)