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 A336107 #11 Sep 17 2020 20:33:07 %S A336107 0,0,0,1,0,0,0,1,1,0,0,2,0,0,0,1,0,2,0,2,0,0,0,4,1,0,1,2,0,0,0,1,0,0, %T A336107 0,4,0,0,0,4,0,0,0,2,2,0,0,5,1,2,0,2,0,4,0,4,0,0,0,6,0,0,2,1,0,0,0,2, %U A336107 0,0,0,9,0,0,2,2,0,0,0,5,1,0,0,6,0,0,0 %N A336107 Number of permutations of the prime indices of n with at least one non-singleton run, or non-separations. %C A336107 A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798. %C A336107 A separation (or Carlitz composition) of a multiset is a permutation with no adjacent equal parts. %F A336107 a(n) = A008480(n) - A335452(n). %F A336107 a(A000961(n)) = 0 if n is in A027883, otherwise 1. %F A336107 a(A005117(n)) = 0. %F A336107 a(n!) = A335459(n). %F A336107 a(A006939(n)) = A022915(n). %e A336107 The a(n) non-separations for n = 12, 36, 60, 72, 180, 420: %e A336107 (11) (112) (1122) (1123) (11122) (11223) (11234) %e A336107 (211) (1221) (1132) (11212) (11232) (11243) %e A336107 (2112) (2113) (11221) (11322) (11324) %e A336107 (2211) (2311) (12112) (12213) (11342) %e A336107 (3112) (12211) (12231) (11423) %e A336107 (3211) (21112) (13122) (11432) %e A336107 (21121) (13221) (21134) %e A336107 (21211) (21123) (21143) %e A336107 (22111) (21132) (23114) %e A336107 (22113) (23411) %e A336107 (22131) (24113) %e A336107 (22311) (24311) %e A336107 (23112) (31124) %e A336107 (23211) (31142) %e A336107 (31122) (32114) %e A336107 (31221) (32411) %e A336107 (32112) (34112) %e A336107 (32211) (34211) %e A336107 (41123) %e A336107 (41132) %e A336107 (42113) %e A336107 (42311) %e A336107 (43112) %e A336107 (43211) %t A336107 primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]]; %t A336107 Table[Length[Select[Permutations[primeMS[n]],MatchQ[#,{___,x_,x_,___}]&]],{n,100}] %Y A336107 A005117 lists positions of zeros, with complement A013929. %Y A336107 A008480 counts permutations of prime indices, ranked by A333221. %Y A336107 A003242 and A335452 count separations, ranked by A333489. %Y A336107 A325535 counts inseparable partitions, ranked by A335448. %Y A336107 A325534 counts separable partitions, ranked by A335433. %Y A336107 Cf. A056239, A112798, A261962, A335451, A335452, A335460, A335489. %K A336107 nonn %O A336107 1,12 %A A336107 _Gus Wiseman_, Sep 03 2020