A175730 Numbers with deficiency of 42.

43, 69, 99, 165, 1168, 1365, 2139136, 32062485, 33722368, 132701205, 8592621568

Offset: 1

Author

Jason G. Wurtzel, Aug 24 2010

Keywords

• nonn
• more

Comments

Numbers with an abundance of -42.

7454198513685 is also in the sequence. - Alexander Violette, Jan 10 2021

Numbers of the form 2^k * (2^(k + 1) + 41) are in the sequence if and only if 2^(k + 1) + 41 is prime. - David A. Corneth, Jan 15 2021

Crossrefs

Cf. A033879 (deficiency).

Programs

PARI

for(n=1, 100000000, if(((sigma(n)-2*n)==-42), print1(n, ", ")))

PARI

is(n)=2*n-sigma(n)==42 \\ Charles R Greathouse IV, Jan 11 2021

PARI

list(lim)=my(v=List()); forfactored(n=1,lim\1, if(2*n[1]-sigma(n)==42, listput(v,n[1]))); Vec(v) \\ Charles R Greathouse IV, Jan 11 2021

Extensions

a(10) from Alexander Violette, Jan 10 2021

a(11) from Charles R Greathouse IV, Jan 15 2021