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

0,2

Links

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

Example

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

Prog

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

Crossrefs

Cf. A000217, A076550.

Sequence in context: A083675 A085076 A076711 * A102428 A128056 A068808

Adjacent sequences: A075085 A075086 A075087 * A075089 A075090 A075091

Keyword

nonn

Author

Amarnath Murthy, Sep 13 2002

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

Status

approved