OFFSET
1,2
MATHEMATICA
Block[{c = Select[Range[10^4], CompositeQ], s}, s = DivisorSigma[1, c]; Most[Length /@ SplitBy[#, # == 0 &]] &@ Array[If[Length@ # == 1, #[[1, 1]], 0] &@ Last@ SplitBy[SortBy[Tally@ Take[s, #], Last], Last] &, Length@ s]] (* Michael De Vlieger, Jul 22 2018 *)
PROG
(PARI) composite(n) = my(i=0); forcomposite(c=1, , i++; if(i==n, return(c)))
mcv(v) = my(w=vecsort(v, , 8), count=vector(#w), ind=0, i=0); for(x=1, #w, for(y=1, #v, if(w[x]==v[y], count[x]++))); for(k=1, #count, if(count[k]==vecmax(count), ind=k; i++)); if(i > 1, return(0), return(w[ind]))
a305671(n) = my(v=[]); for(k=1, n, v=concat(v, sigma(composite(k)))); mcv(v)
terms(n) = my(i=0, j=1); for(k=1, oo, if(a305671(k)==a305671(k+1), j++, if(j > 0, print1(j, ", "); i++; j=1)); if(i==n, break))
terms(20) \\ Print initial 20 terms of the sequence
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Jun 08 2018
STATUS
approved