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%I #38 Aug 27 2018 16:53:36
%S 3,6,210,88200,101970,193290,289680,993990,11264550,59068230,72776970,
%T 98746230,122460690,126500910,132766770,234150930,514442214,531391650,
%U 638082390,650428020,790769790,1249160790,3727074450,4775972850,8299675650,9530202210
%N Psibonacci numbers: solutions n of the equation psi(n) = psi(n-1) + psi(n-2), where psi is the Dedekind psi function (A001615).
%C Analogous to phibonacci numbers (A065557) and other sequences (see crossrefs).
%H Giovanni Resta, <a href="/A291126/b291126.txt">Table of n, a(n) for n = 1..70</a> (terms < 4*10^12)
%e psi(210) = 576 = 240 + 336 = psi(209) + psi(208), therefore 210 is in the sequence.
%t psi[n_]:=If[n < 1, 0, n Sum[ MoebiusMu[ d]^2 / d, {d, Divisors @ n}]];
%t Select[Range[10^6], psi[#]==psi[#-1]+psi[#-2] &]
%Y Cf. A001615, A065557, A065900, A076136, A076251, A145469.
%K nonn
%O 1,1
%A _Amiram Eldar_, Aug 19 2017
%E a(21)-a(26) from _Giovanni Resta_, Aug 26 2018