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 A325638 Numbers n such that sigma(n) can be obtained as the base-2 carryless product of 2n and some k. 4
 6, 28, 456, 496, 6552, 8128, 30240, 31452, 32760, 429240, 2178540, 7505976, 23569920, 33550336, 45532800, 142990848 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers n such that A000203(n) = A048720(2n, k) for some k. Numbers n for which A091255(2n, sigma(n)) = 2n. Conjecture: all terms are even. If this is true, then there are no odd perfect numbers. See also conjectures in A325639 and in A325808. LINKS PROG (PARI) A091255sq(a, b) = fromdigits(Vec(lift(gcd(Pol(binary(a))*Mod(1, 2), Pol(binary(b))*Mod(1, 2)))), 2); A325635(n) = A091255sq(n+n, sigma(n)); isA325638(n) = ((n+n)==A325635(n)); CROSSREFS Cf. A000203, A091255, A325635, A325637, A325808. Subsequence of A325639. Cf. A000396 (a subsequence). Sequence in context: A335290 A173360 A085844 * A331752 A083387 A104511 Adjacent sequences:  A325635 A325636 A325637 * A325639 A325640 A325641 KEYWORD nonn,more AUTHOR Antti Karttunen, May 21 2019 STATUS approved

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Last modified July 8 04:16 EDT 2020. Contains 335504 sequences. (Running on oeis4.)