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A078722
a(n) = prime(n*(n+1)/2+2).
3
3, 5, 11, 19, 37, 59, 83, 113, 163, 211, 269, 337, 409, 487, 587, 673, 787, 907, 1031, 1163, 1301, 1471, 1613, 1789, 1997, 2179, 2381, 2617, 2801, 3049, 3319, 3557, 3821, 4091, 4373, 4673, 4993, 5323, 5651, 5981, 6317, 6691, 7039, 7487, 7853, 8269, 8693, 9109
OFFSET
0,1
COMMENTS
The sum of the reciprocals of the terms appears to converge.
LINKS
MATHEMATICA
Prime[Accumulate[Range[0, 50]]+2] (* Harvey P. Dale, Aug 16 2014 *)
PROG
(PARI) triprimes(n) = { sr = 0; for(j=0, n, x = j*(j+1)/2+2; z = prime(x); sr+=1.0/z; print1(z, ", "); ); print(); /* print(sr); */}
(Magma) [NthPrime(n*(n+1) div 2+2): n in [0..50]]; // Vincenzo Librandi, Jun 08 2016
CROSSREFS
Cf. A000040.
Apart from initial term, primes in second diagonal of triangle in A078721.
Sequence in context: A303005 A320790 A175783 * A320791 A320792 A320793
KEYWORD
nonn,easy
AUTHOR
Cino Hilliard, Dec 20 2002
STATUS
approved