This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A342083 #22 Nov 02 2024 09:14:00 %S A342083 1,1,1,1,1,2,1,2,1,2,1,3,1,2,2,2,1,3,1,3,2,2,1,4,1,2,2,3,1,4,1,3,2,2, %T A342083 2,4,1,2,2,4,1,5,1,3,3,2,1,6,1,3,2,3,1,5,2,4,2,2,1,7,1,2,3,3,2,5,1,3, %U A342083 2,4,1,8,1,2,3,3,2,5,1,6,2,2,1,7,2,2,2 %N A342083 Number of chains of strictly inferior divisors from n to 1. %C A342083 We define a divisor d|n to be strictly inferior if d < n/d. Strictly inferior divisors are counted by A056924 and listed by A341674. %C A342083 These chains have first-quotients (in analogy with first-differences) that are term-wise > their decapitation (maximum element removed). Equivalently, x > y^2 for all adjacent x, y. For example, the divisor chain q = 60/6/2/1 has first-quotients (10,3,2), which are > (6,2,1), so q is counted under a(60). %C A342083 Also the number of factorizations of n where each factor is greater than the product of all previous factors. %H A342083 Amiram Eldar, <a href="/A342083/b342083.txt">Table of n, a(n) for n = 1..10000</a> %F A342083 G.f.: x + Sum_{k>=1} a(k) * x^(k*(k + 1)) / (1 - x^k). - _Ilya Gutkovskiy_, Nov 03 2021 %e A342083 The a(n) chains for n = 2, 6, 12, 24, 42, 48, 60, 72: %e A342083 2/1 6/1 12/1 24/1 42/1 48/1 60/1 72/1 %e A342083 6/2/1 12/2/1 24/2/1 42/2/1 48/2/1 60/2/1 72/2/1 %e A342083 12/3/1 24/3/1 42/3/1 48/3/1 60/3/1 72/3/1 %e A342083 24/4/1 42/6/1 48/4/1 60/4/1 72/4/1 %e A342083 42/6/2/1 48/6/1 60/5/1 72/6/1 %e A342083 48/6/2/1 60/6/1 72/8/1 %e A342083 60/6/2/1 72/6/2/1 %e A342083 72/8/2/1 %e A342083 The a(n) factorizations for n = 2, 6, 12, 24, 42, 48, 60, 72: %e A342083 2 6 12 24 42 48 60 72 %e A342083 2*3 2*6 3*8 6*7 6*8 2*30 8*9 %e A342083 3*4 4*6 2*21 2*24 3*20 2*36 %e A342083 2*12 3*14 3*16 4*15 3*24 %e A342083 2*3*7 4*12 5*12 4*18 %e A342083 2*3*8 6*10 6*12 %e A342083 2*3*10 2*4*9 %e A342083 2*3*12 %t A342083 cen[n_]:=If[n==1,{{1}},Prepend[#,n]&/@Join@@cen/@Select[Divisors[n],#<n/#&]]; %t A342083 Table[Length[cen[n]],{n,100}] %Y A342083 The restriction to powers of 2 is A040039. %Y A342083 Not requiring strict inferiority gives A074206 (ordered factorizations). %Y A342083 The weakly inferior version is A337135. %Y A342083 The strictly superior version is A342084. %Y A342083 The weakly superior version is A342085. %Y A342083 The additive version is A342098, or A000929 allowing equality. %Y A342083 A000005 counts divisors. %Y A342083 A001055 counts factorizations. %Y A342083 A003238 counts chains of divisors summing to n-1, with strict case A122651. %Y A342083 A038548 counts inferior (or superior) divisors. %Y A342083 A056924 counts strictly inferior (or strictly superior) divisors. %Y A342083 A067824 counts strict chains of divisors starting with n. %Y A342083 A167865 counts strict chains of divisors > 1 summing to n. %Y A342083 A207375 lists central divisors. %Y A342083 A253249 counts strict chains of divisors. %Y A342083 A334996 counts ordered factorizations by product and length. %Y A342083 A334997 counts chains of divisors of n by length. %Y A342083 A342086 counts chains of divisors with strictly increasing quotients > 1. %Y A342083 - Inferior: A033676, A066839, A072499, A161906. %Y A342083 - Superior: A033677, A070038, A161908. %Y A342083 - Strictly Inferior: A060775, A070039, A333806, A341674. %Y A342083 - Strictly Superior: A048098, A064052, A140271, A238535, A341673. %Y A342083 Cf. A000203, A001248, A002033, A006530, A018819, A020639, A045690, A337105, A342087, A342094, A342095, A342096, A342097. %K A342083 nonn %O A342083 1,6 %A A342083 _Gus Wiseman_, Feb 28 2021