A011756 - OEIS

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A011756

Prime(n(n+1)/2).

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; text; internal format)

	OFFSET	`1,1`
	LINKS	`_Reinhard Zumkeller_, Table of n, a(n) for n = 1..1000` `Eric Weisstein's World of Mathematics, Triangular Number`
	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, Mar 12 2006`
	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`
	CROSSREFS	`Primes in leading diagonal of triangle in A078721.` `Cf. A000040, A000217, A034953.` `Cf. A195678.` `Sequence in context: A045366 A158708 A093702 * A050950 A218152 A079991` `Adjacent sequences: A011753 A011754 A011755 * A011757 A011758 A011759`
	KEYWORD	`nonn`
	AUTHOR	`Jeff Burch (gburch(AT)erols.com)`
	STATUS	`approved`

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Last modified May 19 00:49 EDT 2013. Contains 225428 sequences.