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A370126
Numbers k for which k’ = x’*y’, where k = x + y with x and y composite, and k’, x’, y’ are the arithmetic derivatives of k, x, y.
2
48, 160, 208, 212, 236, 252, 268, 496, 612, 752, 1040, 1172, 1376, 1476, 1568, 1584, 1692, 1728, 2016, 2192, 2736, 3616, 3627, 3632, 3760, 3932, 4048, 4508, 4572, 5264, 5392, 5900, 6224, 6336, 6640, 6652, 6948, 7376, 7648, 8244, 8928, 9072, 9392, 9712, 10648, 10736, 10960, 12500, 12544, 12592, 12960, 13284, 16452
OFFSET
1,1
LINKS
EXAMPLE
48 is included as 48 = 15+33, and 15' * 33' = 8*14 = 112 = 48' = A003415(48).
1728 (= 2^6 * 3^3) is included as 1728 = 4+1724, and 4' * 1724' = 4*1728 = 6912 = 1728'.
3627 is included as 3627 = 38+3589, and 38' * 3589' = 21*134 = 2814 = 3627'.
PROG
(PARI)
up_to = 2^18;
A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
v003415 = vector(up_to, n, A003415(n));
isA370126(n) = { my(z=v003415[n]); for(x=2, ceil(n/2), if(!isprime(x) && !isprime(n-x) && !(z%v003415[x]), if(z==v003415[x]*v003415[n-x], return(1)))); (0); }; \\ Antti Karttunen, Feb 22 2024
CROSSREFS
Cf. A003415.
Subsequence of A218011.
Sequence in context: A044380 A044761 A248456 * A346293 A244178 A131683
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 21 2024
STATUS
approved