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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).
2
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
1,1
COMMENTS
Numbers k such that k and k+1 are both in A359565.
LINKS
MATHEMATICA
q[n_] := q[n] = Max[Tally[EulerPhi[Divisors[n]]][[;; , 2]]] > 2; Select[Range[3*10^6], q[#] && q[# + 1] &]
PROG
(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); }
CROSSREFS
Subsequence of A359565.
A373530 is a subsequence.
Sequence in context: A115501 A218574 A145871 * A137283 A251875 A156038
KEYWORD
nonn
AUTHOR
Amiram Eldar, Jun 08 2024
STATUS
approved