A081751 - OEIS

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

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OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..49.

EXAMPLE

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

PROG

(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

CROSSREFS

Cf. A081705, A081699.

Sequence in context: A239635 A001041 A216425 * A120360 A120356 A375639

Adjacent sequences: A081748 A081749 A081750 * A081752 A081753 A081754

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

More terms from David Wasserman, Jun 24 2004

STATUS

approved