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A186273 a(n) is the least number k having exactly n representations as m + sigma(m), where sigma(m) is the sum of the divisors of m. 0
2, 11, 95, 3623, 2363, 6143, 21263, 89303, 202703, 472973, 493763, 1013513, 3986483, 3306713, 2364863, 21283763, 19932413, 29391863, 74887313, 98679263, 87499913, 134797163, 201013313, 267843713, 560472413, 775337063, 361823963, 673985813 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..28.

Math Forum, Topic: Petaflop machine not required / n + sigma(n)

EXAMPLE

For the n-th term, the n solutions are

2     {1}

11    {4, 5}

95    {32, 39, 47}

3623  {1687, 1727, 1751, 1811}

2363  {1011, 1099, 1139, 1147, 1181}

6143  {2048, 2631, 2863, 2951, 2983, 3007}

21263 {9111, 10231, 10319, 10447, 10471, 10519, 10631}

89303 {38271, 41671, 42991, 43367, 44287, 44311, 44431, 44651}

MATHEMATICA

nn=1000000; t=Table[n+DivisorSigma[1, n], {n, nn}]; t2=Select[t, # <= 2*nn+1&]; ts=Sort[Tally[t2]]; u=Union[Transpose[ts][[2]]]; c=Complement[Range[Max[u]], u]; If[c != {}, u=Range[c[[1]]-1]]; Table[Select[ts, #[[2]] == n &, 1][[1, 1]], {n, u}]

CROSSREFS

Cf. A007368 (smallest k such that sigma(x) = k has exactly n solutions).

Sequence in context: A266834 A131407 A197994 * A261886 A245895 A231229

Adjacent sequences:  A186270 A186271 A186272 * A186274 A186275 A186276

KEYWORD

nonn

AUTHOR

J. M. Bergot, Feb 16 2011

EXTENSIONS

Corrected and extended by T. D. Noe, Feb 16 2011

a(13)-a(28) from Donovan Johnson, Feb 17 2011

STATUS

approved

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Last modified October 15 15:14 EDT 2019. Contains 328030 sequences. (Running on oeis4.)