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A011756
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Prime(n(n+1)/2).
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5
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2, 5, 13, 29, 47, 73, 107, 151, 197, 257, 317, 397, 467, 571, 659, 769, 883, 1019, 1151, 1291, 1453, 1607, 1783, 1987, 2153, 2371, 2593, 2791, 3037, 3307, 3541, 3797, 4073, 4357, 4657, 4973, 5303, 5641, 5939, 6301, 6679, 7019, 7477
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Reinhard Zumkeller, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Triangular Number
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FORMULA
| a(n) is asymptotic to [n*(n+1)/2] * log [n*(n+1)/2] = [n*(n+1)/2] * [log(n)+log(n+1)-log(2)] ~ (n^2 + n)*(2 log n)/2 ~ (n^2 + n)*(log n). - Jonathan Vos Post (jvospost3(AT)gmail.com), Mar 12 2006
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PROG
| (MAGMA) [NthPrime(n*(n+1) div 2): n in [1..100] ]; // Vincenzo Librandi, Apr 11 2011
(Haskell)
a011756 n = a011756_list !! (n-1)
a011756_list = map a000040 $ tail a000217_list
-- Reinhard Zumkeller, Sep 23 2011
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CROSSREFS
| Primes in leading diagonal of triangle in A078721.
Cf. A000040, A000217, A034953.
Cf. A195678.
Sequence in context: A045366 A158708 A093702 * A050950 A079991 A091270
Adjacent sequences: A011753 A011754 A011755 * A011757 A011758 A011759
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KEYWORD
| nonn
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AUTHOR
| Jeff Burch (gburch(AT)erols.com)
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