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

1,1

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

Prog

(PARI) isA339908(n) = ((n>1)&&(n%2)&&issquarefree(n)&&(bigomega(eulerphi(n))<bigomega(n-1)));

Crossrefs

Cf. A000010, A001222.

Subsequence of A056911 and of A339907, A339911.

Cf. also A339912.

Cf. A339909 (a subsequence).

Sequence in context: A118618 A163411 A335669 * A071595 A225707 A225511

Adjacent sequences: A339905 A339906 A339907 * A339909 A339910 A339911

Keyword

nonn

Author

Antti Karttunen, Dec 21 2020

Status

approved