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A231989
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Least prime p such that f(0),...,f(n) are all primes, where f(0) = p, then f(i+1) = triangular(f(i))+1.
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1
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OFFSET
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1,1
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COMMENTS
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Triangular(p) = p*(p+1)/2 (see A034953).
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LINKS
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EXAMPLE
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a(2) = 3 because 3 is the least prime such that the following are two primes:
p1 = 3 * 4 / 2 + 1 = 7.
p2 = 7 * 8 / 2 + 1 = 29.
a(3) = 43 because 43 is the least prime such that the following are three primes:
p1 = 43 * 44 / 2 + 1 = 947.
p2 = 947 * 948 / 2 + 1 = 448879.
p3 = 448879 * 448880 / 2 + 1 = 100746402761.
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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STATUS
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approved
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