A291176 Numbers k such that s(k) = s(k-1) + s(k-2), where s(k) is the sum of proper divisors of k (A001065).

3, 8, 20, 146139, 584835, 44814015, 1436395095, 9988999095, 25997557299, 193861767939, 2105722150095, 3921293253003, 8234992646643

Offset

1,1

Comments

a(14) > 10^13. - Giovanni Resta, Feb 25 2020

Links

Table of n, a(n) for n=1..13.

Example

s(146139) = 76581 = 75802 + 779 = s(146138) + s(146137), therefore 146139 is in the sequence.

Mathematica

s[n_]:=DivisorSigma[1, n]-n; Select[Range[10^6], s[#]==s[#-1]+s[#-2] &]

Crossrefs

Cf. A001065, A065557, A065900, A076136, A076251, A145469.

Sequence in context: A027320 A027319 A297973 * A066212 A171437 A075719

Adjacent sequences: A291173 A291174 A291175 * A291177 A291178 A291179

Keyword

nonn,more

Author

Amiram Eldar, Aug 19 2017

Extensions

a(7)-a(10) from Giovanni Resta, Aug 29 2017

a(11)-a(13) from Giovanni Resta, Feb 25 2020

Status

approved