A339908 Odd squarefree numbers k > 1 for which bigomega(phi(k)) < bigomega(k-1), where bigomega gives the number of prime divisors, counted with multiplicity.

33, 65, 129, 141, 145, 161, 177, 201, 217, 249, 253, 321, 385, 393, 417, 501, 537, 649, 681, 705, 721, 737, 849, 865, 897, 913, 973, 993, 1041, 1057, 1081, 1101, 1121, 1135, 1149, 1169, 1177, 1281, 1329, 1345, 1401, 1441, 1457, 1473, 1497, 1509, 1537, 1561, 1569, 1585, 1633, 1689, 1729, 1761, 1793, 1821, 1837, 1841

Offset: 1

Author

Antti Karttunen, Dec 21 2020

Keywords

• nonn

Comments

All terms can be found in A339911. Also, all nonmultiples of 3 certainly occur in A339912 also.

The first term of the form 4u+3 is 1135.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..26693; all terms < 2^20

Crossrefs

Cf. A000010, A001222.

Subsequence of A056911 and of A339907, A339911.

Cf. also A339912.

Cf. A339909 (a subsequence).

Programs

PARI

isA339908(n) = ((n>1)&&(n%2)&&issquarefree(n)&&(bigomega(eulerphi(n))