A192282 Numbers n such that n and n+1 have same sum of anti-divisors.

1, 8, 17, 120, 717, 729, 957, 8097, 10785, 12057, 35817, 44817, 52863, 58677, 59757, 76759, 95397, 102957, 114117, 119337, 182157, 206097, 215997, 230037, 253977, 263877, 269277, 271797, 295377, 321417, 402657, 435477, 483117, 485637, 510837, 586797, 589317

Offset

1,2

Comments

Like A002961 but using anti-divisors.

Curiously 957 and 958 have same sum of divisors and same sum of anti-divisors.

Links

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

Example

Anti-divisors of 717 are 2, 5, 6, 7, 35, 41, 205, 287, 478 and their sum is 1066.
Anti-divisors of 718 are  3, 4, 5, 7, 35, 41, 205, 287, 479 and their sum is 1066.

Maple

with(numtheory);
P:=proc(n)
local a, b, i, k;
b:=2;
for i from 4 to n do
  a:=0;
  for k from 2 to i-1 do
    if abs((i mod k)- k/2) < 1 then a:=a+k; fi;
  od;
  if a=b then print(i-1); fi;
  b:=a;
od;
end:
P(200000);

Crossrefs

Cf. A002961, A066272, A192283.

Sequence in context: A177178 A357678 A097405 * A088588 A041537 A153315

Adjacent sequences: A192279 A192280 A192281 * A192283 A192284 A192285

Keyword

nonn

Author

Paolo P. Lava, Jul 27 2011

Extensions

Initial term a(1)=1 inserted, a(2)=9 through a(20)=119337 verified, and a(21)-a(28) added by John W. Layman, Aug 04 2011

Status

approved