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A374223
Numbers k such that sigma(k) and sopfr(k) are both multiples of 3, where sigma is the sum of divisors, and sopfr is the sum of prime factors with repetition.
2
8, 14, 20, 24, 26, 35, 38, 42, 44, 50, 60, 62, 65, 68, 72, 74, 77, 78, 86, 92, 95, 105, 110, 114, 116, 119, 122, 125, 126, 132, 134, 143, 146, 150, 155, 158, 160, 161, 164, 170, 180, 185, 186, 188, 194, 195, 196, 203, 204, 206, 209, 212, 215, 216, 218, 221, 222, 230, 231, 234, 236, 242, 254, 258, 275, 276, 278, 280
OFFSET
1,1
COMMENTS
Numbers such that the multiplicities of prime factors of the forms 3m+1 (A002476) and 3m-1 (A003627) are equal modulo 3, and some of the former has exponent of the form 3k+2, or some of the latter has odd exponent.
If m and n are in the sequence and gcd(m,n)=1, then m*n is also in sequence.
Term k is included <=> term 3*k is included.
LINKS
PROG
(PARI) isA374223 = A374222;
CROSSREFS
Cf. A000203, A001414, A002476, A003627, A374222 (characteristic function).
Indices of multiples of 3 in A374126.
Intersection of A087943 and A289142.
Sequence in context: A264722 A125163 A309355 * A063288 A136798 A172182
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jul 08 2024
STATUS
approved