A339819 - OEIS

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A339819

Squarefree numbers k > 1 for which neither 2-adic nor 3-adic valuation of phi(k) exceeds the corresponding valuation of k-1.

2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 33, 37, 41, 43, 47, 53, 59, 61, 67, 69, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 141, 145, 149, 151, 157, 163, 167, 173, 177, 179, 181, 191, 193, 197, 199, 211, 213, 217, 223, 227, 229, 233, 239, 241, 249, 251, 253, 257, 263, 269, 271, 277, 281, 283

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..15620

PROG

(PARI) isA339819(n) = ((n>1)&&issquarefree(n)&&(valuation(eulerphi(n), 2)<=valuation(n-1, 2))&&(valuation(eulerphi(n), 3)<=valuation(n-1, 3)));

CROSSREFS

Cf. A000010, A005117, A007814, A007949.

Subsequence of A339817.

Sequence in context: A358761 A371654 A089063 * A247142 A350342 A369093

Adjacent sequences: A339816 A339817 A339818 * A339820 A339821 A339822

KEYWORD

nonn

AUTHOR

Antti Karttunen, Dec 20 2020

STATUS

approved