A290704 Solutions to 2*x - phi(x) = sigma(x)/2, where phi(x) is the Euler totient function of x.

1680, 4200, 27000, 175392, 282960, 707400, 1668480, 3344544, 5658480, 14146200, 48644064, 90008880, 130110624, 225022200, 357994728, 460763160, 607281696, 1926458352, 3830537880, 5857651296, 7840881216, 8414628480, 8704032876, 8843224500, 14279194512, 29522053080

Offset

1,1

References

Like A099650 but with totient phi(x) replaced by cototient x - phi(x).

Links

Table of n, a(n) for n=1..26.

Example

phi(1680) = 384, sigma(1680) = 5952 and 2*1680 - 384 = 2976 = 5952/2.

Maple

with(numtheory): P:=proc(q) local n; for n from 1 to q do
if 2*n-phi(n)=sigma(n)/2 then print(n); fi; od; end: P(10^9);

Crossrefs

Cf. A000010, A051953, A099650, A111592, A290703.

Sequence in context: A175749 A231548 A179693 * A342876 A175340 A181928

Adjacent sequences: A290701 A290702 A290703 * A290705 A290706 A290707

Keyword

nonn

Author

Paolo P. Lava, Aug 09 2017

Extensions

a(10)-a(26) from Giovanni Resta, Aug 25 2017

Status

approved