OFFSET
1,1
COMMENTS
Are 2 and 91610 the only even terms?
Are there any abundant numbers (A005101) in this sequence?
Numbers k such that k and k+1 have the same deficiency are 1, 145215, and no more below 10^13 (they are a subset of A112645).
Up to a(2214) = 2001876242879 there are no further even terms nor abundant terms. - Giovanni Resta, May 01 2020
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..500
EXAMPLE
MATHEMATICA
def[n_] := 2*n - DivisorSigma[1, n]; Select[Range[10^5], def[#] == def[# + 2] &]
PROG
(PARI) j1=1; j2=1; for(k=3, 50000000, j=k+k-sigma(k); if(j==j1, print1(k-2, ", ")); j1=j2; j2=j) \\ Hugo Pfoertner, May 01 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, May 01 2020
STATUS
approved