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

1,1

Comments

Numbers k such that k and k+1 are both in A359565.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

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.

Cf. A000010, A102190.

Sequence in context: A115501 A218574 A145871 * A137283 A251875 A156038

Adjacent sequences: A373526 A373527 A373528 * A373530 A373531 A373532

Keyword

nonn

Author

Amiram Eldar, Jun 08 2024

Status

approved