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 A335399 Starts of runs of 5 consecutive numbers that have an equal number of unitary and nonunitary divisors (A048109). 2
 146447622, 2259799749, 2559357269, 2647718871, 3660580374, 4262858871, 4708102374, 5188831623, 5341658373, 5494129749, 5728055749, 5876715750, 6127708374, 6455588247, 6608437623, 6612840374, 6617111750, 6689113623, 6722600373, 7456747623, 7923798375, 8272111445 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Do longer runs of consecutive numbers with an equal number of unitary and nonunitary divisors exist for any length of run? Starts of runs of 6 consecutive numbers that have an equal number of unitary and nonunitary divisors, from Giovanni Resta's bfile, 80566783622, 117243671750, 390773539750, 573122731621, 636972066374. - Zak Seidov, Jun 07 2020 LINKS Giovanni Resta, Table of n, a(n) for n = 1..3000 EXAMPLE 146447622 is a term since 146447622, 146447623, 146447624, 146447625 and 146447626 each have an equal number of unitary and nonunitary divisors. 146447622 has 32 unitary divisors and 32 nonunitary divisors, 146447623, 146447625 and 146447626 each have 8 and 8, and 146447624 has 16 and 16. MATHEMATICA q[n_] := DivisorSigma[0, n] == 2^(PrimeNu[n] + 1); v = q /@ Range[5]; seq = {}; Do[v = Append[Drop[v, 1], q[k]]; If[And @@ v, AppendTo[seq, k - 4]], {k, 6, 3*10^8}]; seq CROSSREFS Subsequence of A048109, A335328, A335397 and A335398. Cf. A000005, A034444, A048105. Sequence in context: A224638 A224642 A185855 * A226970 A212470 A180345 Adjacent sequences: A335396 A335397 A335398 * A335400 A335401 A335402 KEYWORD nonn AUTHOR Zak Seidov and Amiram Eldar, Jun 06 2020 STATUS approved

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Last modified September 26 19:16 EDT 2023. Contains 365666 sequences. (Running on oeis4.)