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 A291750 Compound filter: a(n) = P(A003557(n), A048250(n)), where P(n,k) is sequence A000027 used as a pairing function. 20
 1, 4, 7, 8, 16, 67, 29, 19, 18, 154, 67, 80, 92, 277, 277, 53, 154, 94, 191, 173, 497, 631, 277, 109, 50, 862, 75, 302, 436, 2557, 497, 169, 1129, 1432, 1129, 142, 704, 1771, 1541, 214, 862, 4561, 947, 668, 328, 2557, 1129, 179, 98, 236, 2557, 905, 1432, 199, 2557, 355, 3161, 4006, 1771, 2630, 1892, 4561, 564, 593, 3487, 10297, 2279, 1487, 4561, 10297, 2557 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A000203 (sigma(n)) is a function of this sequence, because formula A000203(n) = A092261(n) * A295294(n) can be rewritten as a relation: A000203(n) = A000203(A057521(n)) * A048250(n) / A048250(A057521(n)), where A057521(n) = A064549(A003557(n)), thus A000203(n) is a function of A003557(n) and A048250(n), the values that are packed here into a(n). A001615 (Dedekind's psi) is a function of this sequence, because it can be written as A001615(n) = A003557(n)*A048250(n). LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 FORMULA a(n) = (1/2)*(2 + ((A003557(n) + A048250(n))^2) - A003557(n) - 3*A048250(n)). PROG (PARI) A003557(n) = n/factorback(factor(n)[, 1]); \\ This function from Charles R Greathouse IV, Nov 17 2014 A048250(n) = if(n<1, 0, sumdiv(n, d, if(core(d)==d, d))); A291750(n) = (1/2)*(2 + ((A003557(n)+A048250(n))^2) - A003557(n) - 3*A048250(n)); CROSSREFS Cf. A000027, A000203, A001615, A003557, A048250, A291751 (rgs-version of this filter). Sequence in context: A344581 A270216 A237599 * A007285 A225430 A295325 Adjacent sequences: A291747 A291748 A291749 * A291751 A291752 A291753 KEYWORD nonn AUTHOR Antti Karttunen, Sep 04 2017 STATUS approved

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Last modified December 5 06:26 EST 2022. Contains 358582 sequences. (Running on oeis4.)