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URL: https://oeis.org/A378750

⇱ A378750 - OEIS

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A378750
Dirichlet inverse of A377984, where A377984(n) = 2*sigma(n) - A003961(n).
2
1, -3, -3, 4, -5, 9, -5, 0, 8, 15, -11, -8, -11, 15, 17, 8, -17, -24, -17, -16, 21, 33, -19, 0, 12, 33, 24, -8, -29, -51, -27, 24, 35, 51, 31, 56, -35, 51, 39, 0, -41, -63, -41, -40, -28, 57, -43, 0, 32, -36, 53, -32, -49, -72, 57, 0, 57, 87, -59, 48, -57, 81, -4, 88, 61, -105, -65, -64, 67, -93, -71, 0, -69, 105
OFFSET
1,2
FORMULA
a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A377984(n/d) * a(d).
PROG
(PARI)
A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A377984(n) = (2*sigma(n) - A003961(n));
memoA378750 = Map();
A378750(n) = if(1==n, 1, my(v); if(mapisdefined(memoA378750, n, &v), v, v = -sumdiv(n, d, if(d<n, A377984(n/d)*A378750(d), 0)); mapput(memoA378750, n, v); (v)));
CROSSREFS
Cf. also A378749.
Sequence in context: A239483 A104806 A241442 * A363091 A373721 A043551
KEYWORD
sign
AUTHOR
Antti Karttunen, Dec 09 2024
STATUS
approved