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 A273353 Number of divisors of A067128(n). 2
 1, 2, 2, 3, 4, 4, 4, 6, 6, 6, 8, 8, 9, 10, 12, 12, 12, 12, 12, 12, 16, 16, 18, 20, 20, 24, 24, 24, 24, 24, 24, 24, 24, 24, 30, 32, 32, 36, 36, 40, 40, 48, 48, 48, 48, 48, 48, 48, 48, 60, 64, 64, 72, 72, 72, 80, 80, 84, 90, 96, 96, 96, 96, 96, 96, 96, 96, 96, 100, 108, 120, 120, 120, 128, 128, 144, 144, 144, 144, 144, 160 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Is a(n + 1) / a(n) ~ 1 for large n? Every term in this sequence also appears in A002183, where every element of this sequence occurs exactly once. In A067128 it is asked if A034287 = A067128. If that is the case then this sequence is also the number of divisors of A034287. LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A000005(A067128(n)). MATHEMATICA s = {}; dmax = 0; Do[d = DivisorSigma[0, n]; If[d >= dmax, AppendTo[s, d]; dmax = d], {n, 1, 10^6}]; s (* Amiram Eldar, Jun 07 2019 *) PROG (PARI) is_a067128(n) = my(nd=numdiv(n)); for(k=1, n-1, if(numdiv(k) > nd, return(0))); return(1) for(n=1, 50000, if(is_a067128(n), print1(numdiv(n), ", "))) \\ Felix FrÃ¶hlich, May 24 2016 CROSSREFS Cf. A000005, A002182, A002183, A034287, A067128. Sequence in context: A224709 A309965 A070172 * A259197 A130128 A210556 Adjacent sequences:  A273350 A273351 A273352 * A273354 A273355 A273356 KEYWORD nonn AUTHOR David A. Corneth, May 20 2016 STATUS approved

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Last modified September 20 16:44 EDT 2019. Contains 327242 sequences. (Running on oeis4.)