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Search: id:A081751
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| A081751 |
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a(n) is the smallest number that is precisely n-tuply abundant. |
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1
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| 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
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(24) <= 1290
See A081705 for the definition of n-tuply abundant. - David Wasserman (wasserma(AT)spawar.navy.mil), Jun 24 2004
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FORMULA
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a(n) = smallest number that is precisely n-tuply abundant
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EXAMPLE
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a(3)=78 because 78 is the smallest number that is exactly triply abundant.
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PROGRAM
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(PARI) program by D. Wasserman 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))
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CROSSREFS
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Cf. A081705, A081699.
Sequence in context: A001335 A145899 A001041 this_sequence A120360 A120356 A109745
Adjacent sequences: A081748 A081749 A081750 this_sequence A081752 A081753 A081754
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KEYWORD
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nonn
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AUTHOR
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Gabriel Cunningham (gcasey(AT)mit.edu), Apr 08 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jun 24 2004
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