A172321 Duplicate of A154689.

5, 7, 10, 13, 14, 18, 19, 26, 31, 38, 39, 43, 50, 55, 61, 62, 69, 72, 73, 78, 84, 86, 91, 95, 96, 98, 103, 108, 109, 110, 115, 119, 122, 123, 129, 133, 136, 138, 139, 145, 146, 151, 153, 159, 181, 182, 187, 190, 193, 199, 205

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 20 2010

Keywords

• dead

Comments

Numbers n such that d(n)=d(n-d(n)).

Programs

Mathematica

sndQ[n_]:=Module[{dn=DivisorSigma[0,n]},dn==DivisorSigma[0,n-dn]]; Select[ Range[250],sndQ] (* Harvey P. Dale, Mar 05 2014 *)

PARI

for(n=3,1000,if(numdiv(n)==numdiv(n-numdiv(n)),print1(n,", ")))