A015734 Odd numbers k such that d(k) does not divide phi(k).

25, 27, 75, 81, 121, 189, 225, 275, 289, 297, 343, 363, 405, 425, 513, 529, 567, 575, 605, 621, 725, 729, 825, 837, 841, 867, 1025, 1029, 1053, 1089, 1161, 1175, 1225, 1269, 1275, 1325, 1331, 1377, 1445, 1475, 1539, 1587, 1593, 1681, 1725

Offset

1,1

Links

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

Mathematica

Select[Range[1, 2000, 2], !Divisible[EulerPhi[#], DivisorSigma[0, #]] &] (* Amiram Eldar, May 15 2024 *)

Prog

(PARI) is(k) = if(k%2, my(f = factor(k), d = numdiv(f), p = eulerphi(f)); p % d, 0); \\ Amiram Eldar, May 15 2024

Crossrefs

Intersection of A005408 and A015733.

Cf. A000005 (d), A000010 (phi).

Sequence in context: A129820 A096522 A195351 * A221617 A083806 A239521

Adjacent sequences: A015731 A015732 A015733 * A015735 A015736 A015737

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Offset corrected by Amiram Eldar, May 15 2024

Status

approved