OFFSET
1,2
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
MATHEMATICA
b[_] = 0;
a[n_] := With[{t = 2 n - DivisorSigma[1, n]}, b[t] = b[t] + 1];
Array[a, 105] (* Jean-François Alcover, Jan 10 2022 *)
PROG
(PARI)
up_to = 65537;
ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om, invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om, invec[i], (1+pt))); outvec; };
A033879(n) = (2*n-sigma(n));
v331181 = ordinal_transform(vector(up_to, n, A033879(n)));
A331181(n) = v331181[n];
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jan 11 2020
STATUS
approved