A286605 Restricted growth sequence computed for number of divisors, d(n) (A000005).

1, 2, 2, 3, 2, 4, 2, 4, 3, 4, 2, 5, 2, 4, 4, 6, 2, 5, 2, 5, 4, 4, 2, 7, 3, 4, 4, 5, 2, 7, 2, 5, 4, 4, 4, 8, 2, 4, 4, 7, 2, 7, 2, 5, 5, 4, 2, 9, 3, 5, 4, 5, 2, 7, 4, 7, 4, 4, 2, 10, 2, 4, 5, 11, 4, 7, 2, 5, 4, 7, 2, 10, 2, 4, 5, 5, 4, 7, 2, 9, 6, 4, 2, 10, 4, 4, 4, 7, 2, 10, 4, 5, 4, 4, 4, 10, 2, 5, 5, 8, 2, 7, 2, 7, 7, 4, 2, 10, 2, 7, 4, 9, 2, 7, 4, 5, 5, 4, 4

Offset

1,2

Comments

For all i, j: A101296(i) = A101296(j) => a(i) = a(j).

For all i, j: a(i) = a(j) <=> A000005(i) = A000005(j).

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Mathematica

With[{nn = 119}, Function[s, Table[Position[Keys@ s, k_ /; MemberQ[k, n]][[1, 1]], {n, nn}]]@ Map[#1 -> #2 & @@ # &, Transpose@ {Values@ #, Keys@ #}] &@ PositionIndex@ Array[DivisorSigma[0, #] &, nn]] (* Michael De Vlieger, May 12 2017, Version 10 *)

Prog

(PARI)
rgs_transform(invec) = { my(occurrences = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(occurrences, invec[i]), my(pp = mapget(occurrences, invec[i])); outvec[i] = outvec[pp] , mapput(occurrences, invec[i], i); outvec[i] = u; u++ )); outvec; };
write_to_bfile(start_offset, vec, bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }
A000005(n) = numdiv(n);
write_to_bfile(1, rgs_transform(vector(10000, n, A000005(n))), "b286605.txt");

Crossrefs

Cf. A000005, A007416 (positions of records, and also the first occurrence of each n).

Cf. also A101296, A286603, A286610, A286619, A286621, A286622, A286626, A286378.

Sequence in context: A337454 A289849 A299701 * A035149 A074848 A252505

Adjacent sequences: A286602 A286603 A286604 * A286606 A286607 A286608

Keyword

nonn

Author

Antti Karttunen, May 11 2017

Status

approved