A075088 Smallest triangular number with n prime factors (counted with multiplicity).

1, 3, 6, 28, 36, 120, 528, 2080, 2016, 25200, 32640, 819840, 131328, 7874496, 20476800, 52433920, 8386560, 102767616, 536887296, 2147450880, 26306560000, 16240435200, 116802736128, 34359607296, 2199022206976, 549755289600

Offset: 0

Author

Amarnath Murthy, Sep 13 2002

Keywords

• nonn

Examples

			a(3)=28 because 28 is a triangular number with 3 prime factors: 28 = 2*2*7.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 0..51

Crossrefs

Cf. A000217, A076550.

Programs

PARI

a(n)=if(n<0,0,s=1; while(abs(bigomega(s*(s+1)/2)-n)>0,s++); s*(s+1)/2)

Extensions

More terms from Benoit Cloitre, Sep 17 2002

a(21)-a(24) from Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 15 2004

Edited by Ray Chandler, Dec 17 2004

a(25) from Ray Chandler, Dec 22 2004