A081751 a(n) is the smallest number that is precisely n-tuply abundant.

12, 24, 78, 66, 54, 42, 30, 120, 540, 390, 264, 282, 366, 180, 546, 510, 330, 318, 990, 936, 702, 780, 564, 1290, 870, 528, 312, 168, 222, 150, 138, 5778, 6174, 3432, 3150, 2850, 2190, 8432, 4464, 3472, 2480, 1488, 5430, 6750, 4452, 4396, 4650, 3270, 2712

Offset: 1

Author

Gabriel Cunningham (gcasey(AT)mit.edu), Apr 08 2003

Keywords

• nonn

Comments

See A081705 for the definition of n-tuply abundant. - David Wasserman, Jun 24 2004

Examples

			a(3)=78 because 78 is the smallest number that is exactly triply abundant, with this aliquot chain: 78->90->144->259->45.
		

Crossrefs

Cf. A081705, A081699.

Programs

PARI

LIMIT = 50; A = vector(LIMIT); count = 0; i = 1; while (count < LIMIT, i = i + 1; ab = 0; lastn = i; n = sigma(i) - i; while(ab <= LIMIT && n > lastn, ab = ab + 1; lastn = n; n = sigma(lastn) - n); if(ab <= LIMIT && ab > 0 && A[ab] == 0, A[ab] = i; count = count + 1)); A \\ David Wasserman, Jun 24 2004

Extensions

More terms from David Wasserman, Jun 24 2004