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A048995 Numbers that are not the sum of the nontrivial factors (excluding 1 and n) of some natural number. 8
1, 4, 51, 87, 95, 119, 123, 145, 161, 187, 205, 209, 215, 237, 245, 247, 261, 267, 275, 287, 289, 291, 303, 305, 321, 323, 325, 335, 341, 371, 405, 407, 425, 429, 447, 471, 473, 497, 515, 517, 519, 529, 539, 551, 555, 561, 575, 583, 611, 623, 625, 627, 657 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

MATHEMATICA

a048995[n_Integer] := Module[{t = Table[i, {i, n}], a048050, k},

  a048050[m_] := Plus @@ Take[Divisors[m], {2, -2}];

  Do[

   If[a048050[k] == 0 || a048050[k] > n, Null, t[[a048050[k]]] = 0],

   {k, 2, n^2}];

  Drop[DeleteDuplicates[t], {2}]

]; a048995[660] (* Michael De Vlieger, Nov 30 2014 *)

PROG

(PARI) mx=8479; v=vector(mx); for(i=2, mx^2, ch=sigma(i)-i-1; if(ch<=mx, if(ch>0, v[ch]=1))); c=0; for(i=1, mx, if(v[i]==0, c++; write("b048995.txt", c " " i))) /* Donovan Johnson, Feb 11 2013 */

CROSSREFS

Complement of A048050.

Cf. A005114 (the same property with the sum of proper divisors) and A007369 (the same property with the sum of all divisors).

Sequence in context: A221477 A122464 A226375 * A215639 A320645 A235325

Adjacent sequences:  A048992 A048993 A048994 * A048996 A048997 A048998

KEYWORD

nonn,nice

AUTHOR

Bill Taylor (W.Taylor(AT)math.canterbury.ac.nz)

EXTENSIONS

Corrected and extended by Jud McCranie

STATUS

approved

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Last modified February 21 11:54 EST 2019. Contains 320372 sequences. (Running on oeis4.)