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Search: id:A137205
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| A137205 |
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Numbers n such that abundance(n) + abundance(n+1) = 2. |
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1
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| 215, 923, 944, 1455, 2379, 5355, 6467, 6623, 14099, 23495, 196343, 212795, 1661135, 4070199, 4160919, 4626699, 60464627, 217408415, 248621603, 262792907, 265371335, 613033667, 684241907, 1065360113, 3148946723, 4773647871, 6729842063, 19910536424
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OFFSET
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1,1
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COMMENT
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The abundance of n is defined as the difference between the sum of the aliquot parts of n and n itself.
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FORMULA
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{n: A033880(n)+A033880(n+1)=2}. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 01 2008
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EXAMPLE
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abundance(215) = sum of aliquot parts of 215 - 215 = 49 -215 = -166;
abundance(216) = sum of aliquot parts of 216 - 216 = 384 -216 = 168;
so abundance(215) + abundance(216) = 2.
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MAPLE
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with(numtheory): a:=proc(n) if sigma(n)+sigma(n+1)-4*n=4 then n else end if end proc: seq(a(n), n=1..100000); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 02 2008
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CROSSREFS
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Cf. A033880.
Sequence in context: A120536 A043391 A063358 this_sequence A091289 A085754 A002239
Adjacent sequences: A137202 A137203 A137204 this_sequence A137206 A137207 A137208
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Mar 04 2008
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EXTENSIONS
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Three more terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 01 2008
a(14)-a(28) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 27 2008
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