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A231989 Least prime p such that p(0),...,p(n) are all primes, where p(0) = p, then p(i+1) = triangular(p(i))+1. 1
3, 3, 43, 236367611, 31542795419 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Triangular(p) = p*(p+1)/2.

LINKS

Table of n, a(n) for n=1..5.

EXAMPLE

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 3 numbers are prime:

p1 = 43 * 44 / 2 + 1 = 947.

p2 = 947 * 948 / 2 + 1 = 448879.

p3 = 448879 * 448880 / 2 + 1 = 100746402761.

CROSSREFS

Cf. A000040, A000217, A231847, A231988.

Sequence in context: A082394 A086889 A269909 * A059495 A174325 A290366

Adjacent sequences:  A231986 A231987 A231988 * A231990 A231991 A231992

KEYWORD

nonn,hard,more

AUTHOR

Alex Ratushnyak, Nov 16 2013

STATUS

approved

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Last modified January 17 05:26 EST 2019. Contains 319207 sequences. (Running on oeis4.)