A373529 Numbers k such that k and k+1 both have at least three divisors with the same value of the Euler totient function (A000010).
32319, 111320, 175959, 179360, 191919, 212120, 246519, 254079, 254960, 279279, 319599, 355508, 357399, 398600, 436149, 463239, 512000, 520064, 524799, 542240, 580040, 606879, 657152, 678699, 685880, 701631, 718640, 726920, 739556, 750519, 759759, 775775, 787815
Offset: 1
Keywords
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
q[n_] := q[n] = Max[Tally[EulerPhi[Divisors[n]]][[;; , 2]]] > 2; Select[Range[3*10^6], q[#] && q[# + 1] &]
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PARI
is(k) = vecmax(matreduce(apply(x->eulerphi(x), divisors(k)))[,2]) > 2; lista(kmax) = {my(q1 = 0, q2); for(k = 2, kmax, q2 = is(k); if(q1 && q2, print1(k-1, ", ")); q1 = q2);}
Comments