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A374463
Numbers k such that the odd parts of sigma(k) and A064989(k) are equal, where A064989 shifts the prime factorization one step towards lower primes, and sigma is the sum of divisors function.
2
1, 3, 5, 15, 189, 945, 2125, 6375, 9261, 42550, 46305, 127650, 401625, 936100, 1191400, 2808300, 3574200, 8041950, 19679625, 22469750, 58378600, 58506250, 67409250, 175135800, 175518750, 176922900, 394055550, 494334500
OFFSET
1,2
COMMENTS
Odd terms after 1 form a subsequence of A347391.
If x and y are included, and they are coprime (gcd(x,y) = 1), then x*y is also included.
FORMULA
{k | A000265(sigma(k)) = A000265(A064989(k))}.
EXAMPLE
945 = 3^3 * 5 * 7 is included as A064989(945) = 2^3 * 3 * 5 = 120, and sigma(945) = 1920 = 2^7 * 3 * 5, with A000265(120) = A000265(1920) = 15.
PROG
(PARI) isA374463(n) = (A000265(sigma(n)==A000265(A064989(n))));
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Antti Karttunen, Jul 11 2024
STATUS
approved