This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A332974 #8 May 09 2020 06:35:03 %S A332974 3,21,321,1257,3237,146139,268713,584835,26749089,9988999095, %T A332974 25997557299,54449485353,935628578283,2105722150095,3921293253003, %U A332974 8234992646643 %N A332974 Solutions k of the equation s(k) = s(k-1) + s(k-2) where s(k) = usigma(k) - k is the sum of proper unitary divisors of k (A063919). %C A332974 a(17) > 10^13. - _Giovanni Resta_, May 09 2020 %e A332974 21 is a term since s(21) = 11 and s(19) + s(20) = 1 + 10 = 11. %t A332974 usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); s[n_] := usigma[n] - n; Select[Range[3, 6*10^5], s[#] == s[# - 1] + s[# - 2] &] %Y A332974 The unitary version of A291176. %Y A332974 Cf. A063919, A065557, A065900, A075565, A076136, A145469, A291126, A292033, A294995, A332973. %K A332974 nonn,more %O A332974 1,1 %A A332974 _Amiram Eldar_, Mar 04 2020 %E A332974 a(12)-a(16) from _Giovanni Resta_, May 09 2020